pearson iit foundation series the complete series physics

THE COMPLETE SERIES

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Pearson IIT Foundation Series

PhysicsPractice Book

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hysics Practice Book

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Physics Practice Book

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> Provides student-friendly content, application-based problems and hints and explanations to master the art of problem-solving

> Uses a graded approach to generate, build and retain interest in concepts and their applications

Pearson IIT Foundation Practice Book Series is designed to accompany the course-books available in this series. Developed by a team of experienced faculties, this workbook series connects the subjective knowledge to its real world applications through various text and chapter-level problems. Each chapter has a set of assessment tests which are mapped to chapters covered in the course-book. These assessment tests will guide students step-by-step towards understanding the central concept of that particular chapter. These tests are recommended (after class material) for further practice.

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Trishna Knowledge Systems


Physics Practice Book

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ISBN 978-93-528-6767-7 eISBN 978-93-530-6119-7

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Published by Pearson India Education Services Pvt. Ltd, CIN: U72200TN2005PTC057128.

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Preface vii

How to Use the Practice Book ix

Series Chapter Flow x

CHAPTER 1 MEASUREMENTS AND KINEMATICS 1.1

Assessment Test I 1.1Assessment Test II 1.4Assessment Test III 1.7Assessment Test IV 1.10Assessment Test V 1.13Assessment Test VI 1.16

Answer Keys 1.19

CHAPTER 2 DYNAMICS 2.1Assessment Test I 2.1Assessment Test II 2.5Assessment Test III 2.9Assessment Test IV 2.12

Answer Keys 2.14

CHAPTER 3 WAVE MOTION AND SOUND 3.1Assessment Test I 3.1Assessment Test II 3.4Assessment Test III 3.7Assessment Test IV 3.10

Answer Keys 3.12

CHAPTER 4 HEAT 4.1Assessment Test I 4.1Assessment Test II 4.4

Assessment Test III 4.7Assessment Test IV 4.10

Answer Keys 4.12

CHAPTER 5 LIGHT 5.1Assessment Test I 5.1Assessment Test II 5.4Assessment Test III 5.8Assessment Test IV 5.11

Answer Keys 5.14

CHAPTER 6 ELECTRICITY 6.1Assessment Test I 6.1Assessment Test II 6.5Assessment Test III 6.9Assessment Test IV 6.12

Answer Keys 6.15

CHAPTER 7 MAGNETISM AND OUR UNIVERSE 7.1

Assessment Test I 7. 1Assessment Test II 7. 4Assessment Test III 7. 7Assessment Test IV 7.10

Answer Keys 7.12

HINTS AND EXPLANATIONS A.1

Contents

Preface

Pearson IIT Foundation Practice Book Series is designed to accompany the course-books available in this series. Developed by a team of experienced faculties, this workbook series connects the subjective knowledge to its real world applications through various text and chapter level problems. Each chapter has a set of assessment tests which are mapped to chapters covered in the course-book. These worksheets will guide students step-by-step towards understanding the central concept of that particular chapter. These tests are recommended as after class material for further practice.

Any suggestions for added or updated additional readings would also be welcome. Students can share their feedback at [email protected].

Many times, students face significant challenges in answering application level questions in Physics, Chemistry and Mathematics. These Practice Books will enhance their problem-solving skill which will definitely lead to a strong subject foundation. The entire practice book series are recommended to be used alongside IIT Foundation course-books.

Students can refer the following steps while using the practice books:

Studychapters fromIIT FoundationCourse-books

Solve thechapter-end

exercises

Solve oneAssessment

Test related tothe chapter

Check selfprogress

Completeremaining

AssessmentTests

How to Use the Practice Book

While preparing for Foundation courses, students need to learn the fundamental concepts with utmost clarity. In order to successfully complete the IIT Foundation course, one must prepare profoundly. Consistent hard work, practice and perseverance are needed throughout the year.

During any competitive examination, one must exercise clinical precision with speed since the average time available to respond to a question is hardly a minute. The aspirants should be conceptually excellent in the subject owing to the negative marking in the examination. A better practice to solve the paper would be to go for the easiest questions first and then gradually progress to the more complicated ones.

Regular practice of MCQs will assist the aspirants in preparing for the examination. In a nutshell, hard work, conceptual clarity and self-assessment are the essential ingredients to achieve success in competitive examinations. IIT Foundation course-books play an important role in understanding the concepts. Student need to read-up on all concepts/theories in a regular and systematic manner.

Class 7

Class 9

Modern Physics

12

Electricity

10

Hydrostatics

6

Kinematics

2

1

Measurements

3

Dynamics

5

Gravitation

Wave Motion and Sound

8

7

Heat

9

Light

11

Magnetism

Simple Machines

4

Course-book Chapter Flow

8

Our Universe

6

Electricity

Light

4

Machines and Tools

7

3

HeatMeasurements

1

Kinematics

2

5

Sound

xiCourse-book Chapter Flow

Class 8

Class 10

Light

4

Electronics

11

Modern Physics

9


6

Dynamics

2

1

Kinematics

3

Heat

5

Hydrostatics

Electromagnetism

87

Electricity

10

Sources of Energy

5


10

Electromagnetism

Magnetism

9

8

Electricity

6

Heat

3

Dynamics

Kinematics

2

1

Measurements

11

Sources of Energy

Hydrostatics

4

Light

7

Assessment Test I Time: 30 min.

Directions for questions from 1 to 15: Select the correct answer from the given options.

1. Assertion (A): The mass of the body decreases as it moves to higher altitudes. Reason (R): The value of g decreases as we move to higher altitudes. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

2. Assertion (A): The SI unit of acceleration is m s–2. Reason (R): Acceleration is the rate of change in velocity. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

3. Arrange the following steps in the proper sequence to calculate the volume of an irregular-shaped stone.

(A) Immerse the stone into the vessel and note the difference in the volume of the liquid. (B) Take a stone (irregular shaped) and a measuring cylindrical jar. (C) Pour a liquid like water into the jar and note the volume of the liquid. (D) The volume of the stone is equal to the increase in the volume of the

liquid. (a) ABCD (b) BCAD (c) DBCA (d) DCBA

4. A hockey player hits the ball moving with a speed of 50 m s–1 in its same direction. Because of this the velocity increases to 60 m s–1 in 0.1 s. Arrange the following steps in sequential order to calculate the acceleration of the ball.

1

Space for rough work

Measurements and Kinematics

Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Measurements; Page number - 1.1–1.10; Chapter - Kinematics; Page number - 2.1–2.16

Chapter 1 Measurements and Kinematics 1.2

Space for rough work (A) Find the initial velocity of the ball and the velocity of the ball at the end of 0.1 s after it is being hit.

(B) Write down the required equation of motion as v = u + at, where v, u, a and t are final velocity, initial velocity, acceleration and time, respectively.

(C) Substitute the given values in the above equation and obtain the value of a.

(D) Get the value of a as v u

t−

(a) ABDC (b) BDAC (c) DBAC (d) ADBC

5. Match the statements of Column A with those of Column B.

Column A Column B

(A) Physical quantity (a) Volume of a drop of liquid

(B) Burette (b) Measurable quantity

(C) Instantaneous speed (c) Rate of change of velocity

(D) Acceleration (d) m s–1

(a) A → b; B → a; C → d; D → c

(b) A → a; B → b; C → c; D → d (c) A → d; B → c; C → b; D → a (d) A → d; B → c; C → a; D → b

6. For a given vernier caliper, one M.S.D. = 1

10cm and the number of divisions

of vernier scale is = 20. What is the least count of the vernier caliper? (a) 0.05 cm (b) 0.5 mm (c) 0.05 mm (d) 0.02 cm

7. One centimeter of main scale of a vernier caliper is divided into 10 equal parts. M.S.R and V.C.D observed while measuring the length of an object are 3 and 4, respectively. Then, the length of the object is _________ mm. (Take number of division on vernier scale as 10).

(a) 4.3 (b) 3.4 (c) 3.04 (d) 4.03

8. The CGS unit of average speed is _________. (a) m s–1 (b) cm s–1 (c) ft s–1 (d) km h–1

9. The density of gold is 19 g cm–3. Then, the relative density is _________.

(a) 19

1000kg m–3 (b) 19,000 kg m–3

(c) 19 (d) 191000

Assessment Test I 1.3

Space for rough work 10. A car is moving with 120 km h–1. On seeing a speed breaker, the driver applies the brakes and stops the car in 4 s. What is the value of the deceler-ation produced in the car is _________ m s–2.

(a) −175

5 (b) +

253

(c) −325

(d) −253

11. An athlete completes running track of length 330 m in 40 s and comes back to his original position. Find the average velocity of the athlete.

(a) 5 m s–1 (b) 0 m s–1

(c) 334

m s–1 (d) 332

m s–1

12. An aeroplane is moving with a uniform velocity of 800 km h–1, then its _________.

(a) average velocity is 800 km h–1

(b) instantaneous velocity is 800 km h–1

(c) acceleration is zero (d) displacement is zero

13. A car travels the first hour with 50 km h–1 and the second hour with 100 km h–1. What is the average speed of the car?

(a) 120 km h–1 (b) 100 km h–1

(c) 150 km h–1 (d) 75 km h–1

14. A body travels 100 m in 10 s. Then, (A) the average velocity of the body is 10 m s–1 only when the body travels

in a straight path. (B) the average speed of the body is 10 m s–1 irrespective of its direction of

motion. (a) Only A is true. (b) Only B is true. (c) Both A and B are true. (d) Both A and B are false.

15. A bus starts from the rest and moves with uniform acceleration 2 m s–2 for 10 s. The average velocity of the bus is _________.

(a) 10 m s–1 (b) 20 m s–1

(c) 0 m s–1 (d) 40 m s–1


Space for rough workAssessment Test II Time: 30 min.


1. Assertion (A): The mass of a body remains the same everywhere in the universe.

Reason (R): Mass is the inherent property of the body. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

2. Assertion (A): The average speed of the vehicle is equal to the average velocity of the vehicle.

Reason (R): The vehicle is moving in a straight path. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

3. Arrange the following steps in the proper sequence to find the radius of a metallic sphere using standard vernier caliper.

(A) Note M. S. R and V. S. R from the given data. (B) Place the metallic sphere between the jaws of a vernier caliper. (C) Here diameter, (D) = M. S. R + (V. S. R × L. C). (D) Substitute the values and obtain the diameter of the sphere. (F) The radius of the metallic sphere is equal to half the diameter. (a) BACDE (b) EABCD (c) AEDCB (d) DECAB

4. An MMTS train moving with 90 km h–1 speed retards uniformly and comes to a halt by covering 200 m. Arrange the following steps in sequential order to calculate the time taken by the train to come to a halt.

(A) Substitute the values of u, v and s in the above formula. (B) Write down the given data and convert the values into SI system of unit. (C) Write the equation of motion u v s

t2+

= , where u, v, s and t are initial

velocity, final velocity, displacement and time taken, respectively. (D) Obtain the value of t. (a) DABC (b) BCAD (c) BCDA (d) CABD

Assessment Test II 1.5

Space for rough work 5. Match the statements of Column A with those of Column B.

Column A Column B

(A) Derived quantity (a) Ampere (A)

(B) Displacement (b) Hardware shop

(C) Roman steel yard (c) Vector quantity

(D) Fundamental unit (d) Velocity.

(a) A → d; B → c; C → b; D → a (b) A → a; B → d; C → b; D → c (c) A → b; B → a; C → d; D → b (d) A → b; B → d; C → a; D → c

6. While measuring the length of an object, using vernier caliper, the M. S. R

and V. C. D. were observed to be 22 and 8, respectively. If 1 M. S. D. = 12

mm

and L. C. = 0.05 mm, the length of the object is _________.

(a) 0.14 mm (b) 1.14 mm (c) 11.4 cm (d) 11.4 mm

7. In a vernier caliper, 2 cm on main scale is divided into 20 equal parts and 1 V. S. D is equal to 0.9 mm. What is the least count of the vernier caliper?

(a) 0.1 cm (b) 0.1 mm (c) 1 mm (d) 0.01 mm

8. The CGS unit of amount of substance is _________. (a) Mol (b) Kelvin (c) Candela (d) non-existent

9. A stone of density 6 g cm–3 can be used as a sinker in a liquid of density _________.

(a) 11 × 103 kg m–3 (b) 7 g cm–3

(c) 2000 kg m–3 (d) 6000 kg m–3

10. A ball is rolling with a velocity 20 m s–1 on a cement floor and stops in 10 s. What is the acceleration produced in the ball?

(a) –20 m s–2 (b) –200 m s–2

(c) –2 m s–2 (d) +20 m s–2

11. A fan blade of length 13

m moving with uniform velocity makes 1000 rota-

tions in 20 s. Calculate the average velocity of the fan at the end of 20 s. (a) 0 m s–1 (b) 50 m s–1

(c) 50 π m s–1 (d) 13

π m s–1


Space for rough work 12. A toy car moves along the length and breadth of a rectangle as shown in the figure given below. If the length of the rectangle is 4 m, then find the ratio of displacement to distance covered by the car.

C

B 4 m

A

5 m

D

(a) 53

(b) 75

(c) 57

(d) 54

13. A cyclist moves the first-half of the distance with 10 km h–1 speed and the second-half of the distance with speed V km h–1. If the average speed of the cycle is 15 km h–1, then the value of V is _________ km h–1.

(a) 5 (b) 15 (c) 20 (d) 30

14. A body is moving in a straight path. Then, (a) its instantaneous speed is equal to its instantaneous velocity. (b) its average speed is equal to its average velocity. (c) its acceleration is equal to a change in its velocity. (d) Both (a) and (b).

15. A person starts from his house on his bike at 9 a.m. and returns to his house and at 8 p.m. If the odometer reading at 9 a.m. is 4700 km and the average speed of the bike is 20 km h–1, then the odometer reading of the bike at 8 p.m. is _________ km.

(a) 4900 (b) 4920 (c) 4970 (d) 4810

Assessment Test III 1.7

Space for rough workAssessment Test III Time: 30 min.


1. Which of the following physical quantities has Candela as its unit? (a) Amount of substance (b) Temperature (c) Luminous intensity (d) Electric current

2. What is the least count of a vernier caliper whose 1 M.S.D. is 1 mm and 20 V.S.D. = 19 mm?

(a) 0.1 mm (b) 0.01 mm (c) 0.05 mm (d) 0.5 mm

3. Which of the following is true with respect to a standard vernier calipers? (a) N vernier scale divisions = (N – 2) main vernier scale divisions. (b) N vernier scale divisions = (N + 1) main scale divisions. (c) N vernier scale divisions = (N – 1) main scale divisions. (d) N main scale divisions = (N) vernier scale divisions.

4. If the relative density of ice is 0.9, its density is _________ kg m–3. (a) 0.9 (b) 900 (c) 9000 (d) 9

5. When 20 drops of a liquid are drained from a burette, the initial and final volumes of the liquid are found to be 10 mL and 50 mL, respectively. What is the volume of 1 drop of the liquid?

(a) 0.5 mL (b) 1 mL (c) 4 mL (d) 2 mL

6. The unit of pressure is pascal in SI system. If 1 pascal is equal to 1 kg m–1 s–2, then 1 pascal = _________ g cm–1 s–2.

(a) 10 (b) 100 (c) 1000 (d) 1


Column A Column B

(A) Length (p) ampere

(B) Electric current (q) year

(C) Time (r) mile

(a) A → q; B → p; C → r (b) A → p; B → q; C → r

(c) A → r; B → p; C→ q (d) A → q; B → r; C → p


Space for rough work 8. An object of volume 100 cm3 and another of volume 150 cm3, when placed on the either sides of a physical balance, balance each other. Find the ratio of their densities.

(a) 35

(b) 32

(c) 87

(d) 12

9. Find the area of shaded region in the figure given below.

2 cm

2 cm

5 cm

radius = 1 cm

•

(a) 11.86 cm2 (b) 9.8 cm2

(c) 17.23 cm2 (d) 23.81 cm2

10. The viscous force in case of a liquid is given by, F η= Avx

. Where A = area, v = velocity, x = distance and η is a constant. What is the

unit of η? (a) N m s–1 (b) N m–2 s–1

(c) N m–2 s (d) N m3 s–1

11. A cylinder of unknown radius was held between the lower jaws of a ver-nier caliper. The main scale is divided into millimeters and vernier scale has 20 divisions. The vernier coinciding division is 16. If the zeroth division of the vernier scale lies between 12.3 cm and 12.4 cm of the main scale, the radius is _________ mm.

(a) 41.9 (b) 61.9 (c) 81.8 (d) 88.5

12. The SI unit of a physical quantity is kg m s–2, then the ratio of SI and CGS unit of the quantity is _________.

(a) 10–5 (b) 10–2 (c) 102 (d) 105

13. If the principle used to construct a vernier caliper is N V.S.D. = (N – 2) M.S.D., its least count is _________ mm. (1 M.S.D. = 1 mm and N = 10)

(a) 0.1 (b) 0.01 (c) 0.2 (d) 0.3

14. When an object is immersed into water, the volume of the water displaced is 200 cm3. What is the relative density, if the mass of the object is 400 g?

(a) 2 (b) 0.5 (c) 40 (d) 8


Space for rough work 15. When an object is placed between the jaws of a vernier caliper, the zero of the vernier scale is found to be on the right of 7th division of the main scale. The 8th division of the vernier scale is found to coincide with one of the divi-sions of the main scale. Arrange the following steps in sequential order to determine the length of the object. [1 M.S.D. = 1 mm, number of V.S.D. = 10]

(A) Determine the length of the object (B) Use the formula M.S.R. + V.C.D. × L.C. (C) Note the M.S.R., V.C.D., 1 M.S.D. and number of V.S.D. (D) By using the information given determine the least count. (a) ACBD (b) CDBA (c) DBCA (d) ACDB


Space for rough workAssessment Test IV Time: 30 min.


1. The speedometer of a vehicle indicates its _________. (a) instantaneous speed. (b) average speed. (c) instantaneous velocity. (d) average velocity.

2. Calculate the value of 5 m s–1 in km h–1. (a) 10 (b) 1.38 (c) 18 (d) 3.6

3. If a body is moving with uniform velocity, then its acceleration is _________. (a) uniform (b) negative (c) positive (d) zero

4. The slope of a displacement-time graph is _________. (a) velocity (b) speed (c) acceleration (d) distance

5. Assertion (A): Velocity is a vector. Reason (R): Velocity has both magnitude and direction. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.


Column A Column B

(A) Uniform velocity Derived quantity

(a) Total distance ÷ time

(B) Average speed (b) m s–2

(C) Average velocity (c) Acceleration is zero

(D) Acceleration (d) Ratio of total displacement to total time taken

(a) A → c; B → a; C → d; D → b (b) A → a; B → c; C → b; D → d (c) A → c; B → a; C → b; D → d (d) A → a; B → b; C → c; D → d

Assessment Test IV 1.11

Space for rough work 7. A car starts from rest and moves along a straight line with an acceleration of 6 m s–2. The displacement of the car in fourth second is _________ m.

(a) 48 (b) 21 (c) 0 (d) 20

8. A particle moved 8 m towards west and then moved 13 m towards east. What is the total distance travelled and the magnitude of displacement?

(a) 8 m and 8 m (b) 21 m and 5 m (c) 21 m and 8 m (d) 21 m and 13 m

9. A person on a rotating platform of radius 7 m, makes 3 rotations in 4 min. What is the magnitude of the displacement of the person (in m)?

(a) 28 (b) 0 (c) 14 (d) 176

10. A boy kicks a football horizontally from the roof of a building of height 6 m. If the line joining the initial position of the football and the point where it hits the ground makes an angle of 45° with the ground, then the displace-ment of the football is _________ m.

(a) 6 (b) 6 2

(c) 12 m (d) 3

11. A car moving with a constant acceleration covers 24 m in 4 s and 21 m in the next 2 s. What is the initial velocity of the car?

(a) 3 km h–1 (b) 3 m s–1

(c) 1.5 km h–1 (d) 1.5 m s–1

12. A car starts moving with uniform acceleration from its position of rest and it moves 100 m in 10 s. On applying brakes, it stops after covering 50 m. Then magnitude of acceleration in the second part of its motion is _________ m s–2.

(a) 20 (2) 200 (c) 40 (4) 4

13. Which of the following graphs is impossible with respect to velocity-time graph?

(a)

0 t

V

X

Y (b)

0 t

V

X

Y

(c)

0 t

V

X

Y (d)

0 t

V

Y

X


Space for rough work 14. A passenger is at a distance 10 m from a bus when the bus starts with a constant acceleration of 0.1 m s–2. The velocity with which the passenger should run towards the bus so as to catch the bus in 30 s is _________.

(a) 2.5 m s–1 (b) 2 m s–1

(c) 3.5 m s–1 (d) 1.83 m s–1

15. Starting from rest a car moves with a uniform acceleration and attains a velocity of 10 m s–1 in 10 s. It then moves with uniform speed for 15 s and is then brought to rest in 12 s under uniform retardation. Arrange the fol-lowing steps in sequential order to find the total distance covered using v-t graph.

(A) Add the area of triangles and rectangles. (B) Find the area under triangles and rectangles. (C) Draw the velocity-time graph by using the information given in the

question. (D) Divide the graph into triangles and rectangles. (a) ACBD (b) CDAB (c) BACD (d) CDBA

Assessment Test V 1.13

Space for rough workAssessment Test V Time: 30 min.


1. Which of the following is the SI unit of luminous intensity? (a) Gram (b) Mole (c) Candela (d) Kelvin

2. Determine the number of vernier scale divisions required for a vernier cali-per, so that the least count is 0.05 mm. (I M.S.D. = 1 mm)

(a) 40 (b) 30 (c) 10 (d) 20

3. Which of the following is incorrect with respect to a standard vernier caliper?

(a) =L.C1 M.S.D.

N (b) L.C = 1 M.S.D. – 1 V.S.D.

(c) L.C =1 M.S.D.1 V.S.D.

(d) 1 M.S.D. = 1 mm

4. If the relative density of iron is 5, its density is _________ g cm–3. (a) 5 (b) 5000 (c) 500 (d) 50000

5. The volume of a drop of a liquid is 0.3 mL. When 30 drops of the liquid are drained, the level of the liquid in the burette is found to be 50 mL. What is the initial level of the liquid?

(a) 150 mL (b) 59 mL (c) 50 mL (d) 200 mL

6. The unit of momentum in SI system is kg m s–1. Then 1 SI unit of momentum is equal to _________ CGS units of momentum.

(a) 102 (b) 103 (c) 104 (d) 105


Column A Column B

(A) amu (p) foot

(B) Time (q) unit of mass

(C) Length (r) day

(a) A → p; B → q; C → r (b) A → r; B → p; C → q (c) A → q; B → r; C → p (d) A → p; B → r; C → r


Space for rough work 8. When two objects A and B are separately dropped into the water, the vol-ume of water displaced is found to be the same. What is the ratio of the densities, if the masses of A and B are in the ratio 2 : 3, respectively?

(a) 2 : 3 (b) 3 : 2 (c) 3 : 1 (d) 1 : 3

9. Find the area of unshaded region in the figure given below.

10 cm

radius = 3.5 cm

7 cm

3 cm

2 cm

(a) 172.5 cm2 (b) 85.3 cm2

(c) 64.3 cm2 (d) 108.3 cm2

10. The expression for a physical quantity isµT

, where T = Force and

μ =mass

length. What is the physical quantity?

(a) mass (b) speed (c) time (d) distance

11. 1 M.S.D. of a vernier caliper is 1 mm and the number of vernier scale divi-sions is 40 and the vernier coinciding division is 28. What is the length of the object, if zeroth division of the vernier scale lies between 11.2 cm and 11.3 cm?

(a) 1137 (b) 112.7 (c) 142.8 (d) 11.3

12. The SI unit of a quantity is kg m2, its CGS unit is _________. (a) g cm2 (b) g cm–2

(c) g–1 cm–2 (d) g–1 cm3

13. The number of vernier scale divisions choosen in a vernier calipers is 10, 1 M.S.D. = 1 mm, and the least count is 0.3 mm, then the principle used to design the vernier caliper is _________.

(a) (N) V.S.D. = (N – 1) M.S.D.

(b) (N) V.S.D. = (N – 2) M.S.D.

(c) (N) V.S.D. = (N – 3) M.S.D.

(d) (N) V.S.D. = N M.S.D.

Assessment Test V 1.15

Space for rough work 14. When an object floats on the surface of a liquid, half of the volume is immersed into the liquid. If the volume of the liquid displaced by it is 500 cm3 and mass of the object is 500 g, determine the density of the liquid.

(a) 1 g cm–3 (b) 0.5 g cm–3

(c) 2 g cm–3 (d) 4 g cm–3

15. The length of an object measured by using a vernier caliper is 6.3 mm. If the V.C.D. = 3, 1 M.S.D. = 1 mm and N = 10, arrange the following steps to determine the main scale reading in proper sequence.

(A) Use the formula, length = M.S.R. + V.C.D. × L.C. (B) Determine the least count. (C) Note the values of V.C.D., M.S.D. and number of vernier scale divisions. (D) Determine the M.S.R. (a) BACD (b) CBAD (c) ACBD (d) BCAD


Space for rough workAssessment Test VI Time: 30 min.

Direction for questions from 1 to 15: Select the correct answer from the given options.

1. The odometer of a car measure its _________. (a) speed (b) distance (c) displacement (d) Both (b) and (c)

2. 18 km h–1 = _________ m s–1

(a) 18 (b) 5 (c) 18000 (d) 0.018

3. If a body is moving with an increasing velocity, then its acceleration is _________.

(a) negative (b) positive (c) zero (d) None of the above

4. Slope of velocity-time graph gives _________. (a) velocity (b) displacement (c) speed (d) acceleration

5. Assertion (A): Time is a scalar quantity. Reason(R): Time has both magnitude and direction. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.


Column A Column B

(A) Area under acceleration-time graph (a) Velocity

(B) Area under velocity-time graph (b) Acceleration

(C) Slope of velocity-time graph (c) Displacement

(a) A → a; B → c; C → b (b) A → b; B → c; C → b (b) A → c; B → a; C → b (d) A → c; B → a; C → c

Assessment Test VI 1.17

Space for rough work 7. If a bus starts from rest, moving along a straight line and travelling with an acceleration of 8 m s–2, then the displacement in the third second is _________ m.

(a) 3.1 (b) 0.32 (c) 20 (d) None

8. A particle moved 10 m towards east and then moved 10 m towards north. The magnitude of the displacement and the total distance covered are _________ and _________, respectively.

(a) 10 2 m, 20 m (b) 20 m, 20 m

(c) 20 m, 10 2 m (d) 10 m, 20 m

9. A person on a merry–go–round of radius 7 m makes 112

rotations in

4 s. What is the average velocity of the person (in m s–1)? (a) 14 (b) 16.5 (c) 3.5 (d) 3

10. A boy kicks a football from the top of a building of height 10 m. If the line joining the initial position of the football and the point where it hits the ground makes an angle of 45° with the ground, then find the distance of point where it hits the ground from the foot of the building.

(a) 10 2 m (b) 20 m (3) 10 1 2+( ) m (4) 10 m

11. A car moving with constant acceleration of 1.5 m s–2 covers x m in 4 s and 21 m in the next 2 s. The initial velocity of the car is 3 m s–1. Calculate the value of x.

(a) 2.4 m (b) 24 cm (3) 24 m (4) 24 cm

12. The velocity-time graph of a body is shown below. Which among the follow-ing is the displacement time graph of the body?

t

V

X

Y

(a)

t

s

X

Y (b)

t

S

X

Y



(c)

t

S

X

Y

(d)

t

S

X

Y

13. A car starts moving with a uniform acceleration from its position of rest and it moves 25 m in 3 s. On applying brakes, it stops after covering a distance

d. What is the value of d, if its deceleration is 509

m s–2?

(a) 509

m (b) 25 m (c) 503

m (d) 50 m

14. A person is at a distance of d m from a bus when the bus starts with a uni-form acceleration of 0.05 m s–2. The velocity with which the person should run towards the bus is 1.5 m s–1 to catch the bus in 40 s. Find the value of d.

(a) 50 m (b) 10 m (c) 20 m (d) 40 m

15. Starting from rest, a car moves with a uniform acceleration and attains a velocity of 20 m s–1 in 5 s. It then moves with a uniform speed for 10 s and is then brought to rest in t seconds under uniform retardation. Arrange the following steps to find t using a v – t graph, if total distance covered is 380 m.

(A) Add the area of triangles and rectangles. (B) Find the area under triangles and rectangle. (C) Draw the velocity-time graph by using the information given in the

question. (D) Divide the graph into triangles any rectangles. (a) ACBD (b) CDBA (c) CBDA (d) CABD

Answer Keys 1.19

Answer Keys

Assessment Test I 1. (d) 2. (a) 3. (b) 4. (a) 5. (a) 6. (c) 7. (b) 8. (b) 9. (c) 10. (b) 11. (b) 12. (d) 13. (d) 14. (c) 15. (a)

Assessment Test II 1. (a) 2. (a) 3. (a) 4. (b) 5. (a) 6. (d) 7. (b) 8. (d) 9. (c) 10. (a) 11. (a) 12. (c) 13. (d) 14. (d) 15. (b)

Assessment Test III 1. (c) 2. (c) 3. (c) 4. (b) 5. (d) 6. (a) 7. (c) 8. (b) 9. (a) 10. (c) 11. (b) 12. (d) 13. (c) 14. (a) 15. (b)

Assessment Test IV 1. (a) 2. (c) 3. (d) 4. (a) 5. (a) 6. (a) 7. (b) 8. (b) 9. (b) 10. (b) 11. (b) 12. (d) 13. (a) 14. (d) 15. (d)

Assessment Test V 1. (c) 2. (d) 3. (c) 4. (a) 5. (b) 6. (d) 7. (c) 8. (a) 9. (a) 10. (b) 11. (b) 12. (a) 13. (c) 14. (b) 15. (b)

Assessment Test VI 1. (b) 2. (b) 3. (b) 4. (d) 5. (d) 6. (a) 7. (c) 8. (a) 9. (c) 10. (d) 11. (c) 12. (b) 13. (b) 14. (c) 15. (b)



1. Arrange the following steps in sequential order to find the shift in the height of centre of gravity, when a rectangular lamina resting on the longer side is rotated by 90° in vertical plane.

(A) When the rectangular lamina is resting on longer side, the height of cen-

tre of gravity (h) is equal to half of the breadth

b2

of the rectangle.

(B) Let the dimensions of the rectangular lamina be length () and breadth (b).

(C) When the rectangular lamina is rotated by 90° in the vertical plane, it is resting on the shorter side (breadth).

(D) The shift in the position of centre of gravity is equal to the difference in h and h’.

(E) When the rectangular lamina is resting on the shorter side, the height of

centre of gravity (h’) is equal to half of the length 2

of the rectangle.

(a) BACED (b) BEDAC (c) BCADE (d) BECAD

2. The velocity of a body changes from x m s–1 to y m s–1 in t s under the action of constant external force. Arrange the following steps in sequential order to calculate the magnitude of external force acting on the body.

(A) Determine the change in velocity, (y – x) m s–1. (B) The magnitude of external force acting on the body is m ( )

×−y x

tN.

(C) Let m be the mass of the body. (D) The rate of change in velocity is acceleration of the body, that is,

y xt

m s 2−

− .

(a) CADB (b) DCAB (c) BCAD (d) ABCD

2Space for rough work

Dynamics

Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Dynamics; Page number - 3.1–3.32

Chapter 2 Dynamics 2.2


Column A Column B

(A) Frictional force between highly polished surfaces in contact

(a) Outside the body

(B) Interaction between protons and neutrons

(b) Increases

(C) Centre of gravity of an annular ring (c) Decreases

(D) When a person standing on a swing sits, the height of centre of gravity

(d) Nuclear forces

(e) Within the body

(f) Electromagnetic forces

(a) A → c; B → f; C → e; D → b (b) A → b; B → f; C → e; D → c (c) A → b; B → d; C → a; D → c (d) A → b; B → d; C → e; D → c

4. Assertion (A): The work done by the gravity on an ascending body is negative.

Reason (R): The displacement and gravitational force are opposite in direction.

(a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

5. Assertion (A): When a person swims, he pushes the water in the same direction as his motion.

Reason (R): Both action and reaction act on the same body. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

6. To make two bodies A and B experience an equal acceleration, forces 6 N and 4 N are applied, respectively. If the bodies are combined, then to pro-duce the same acceleration, the force applied should be _______ N.

(a) 1 (b) 3 (c) 6 (d) 10


Space for rough work 7. Weightlessness is experienced by _______. (a) a person during his free fall (b) astronauts on moon (c) a person who experiences reaction force (d) a person during climbing a hill

8. If the mass of a body is increased by 20%, then the momentum of body remains same, if the velocity approximately _______.

(a) decreases by 17% (b) increases by 17% (c) decreases by 83% (d) increases by 32%

9. Two spheres moving in opposite directions along a straight line can inter-change their velocities on colliding with each other, if _______.

(a) the magnitudes of their velocities before collision are equal. (b) their masses are equal. (c) their momenta before collision are equal. (d) their accelerations are equal.

10. A ball of mass 200 g moving with a speed of 2 m s–1 hits a wall normally and bounces back with the same speed. If the ball is in contact with the wall for 2 millisecond, the force exerted on the ball is _______ N.

(a) 200 (b) 400 (c) 600 (d) 800

11. To lift a body vertically up from the surface of the Earth through a certain height, 20 J of work is required. If the same body is lifted up vertically through an equal height on the surface of the Moon, then the work required is _______ J.

=

g

g

6moonearth

(a) 2.22 (b) 3.33 (c) 4.44 (d) 5.65

12. A rod of 4 m length is bent in the form of a square. What is the distance of the centre of gravity to any one of the vertices (in m)?

(a) 1 (b) 2 (c) 12

(d) 13


Space for rough work 13. A load of 10 kg weight is suspended at one end of a lever which is pivoted on a fulcrum at the other end, as shown in the given figure. What should be the effort (P) (in N), if we apply the effort at the centre of lever to balance it? (g = 10 m s–2)

P ℓ

10 kgf

(a) 200 (b) 300 (c) 400 (d) 500

14. If a body of mass 5 kg is dragged along the frictionless inclined plane shown in the figure, then the effort (p) required to drag the body is _______. (g = 10 m s–2)

3 m

4 m

90°

(a) 3 × 106 dyne (b) 30 dyne (c) 3 N (d) 3 × 102 N

15. What is the efficiency of the pulleys, if the pulleys used in following system are frictionless and the string used is massless?

(a) 0.8 (b) 1 (c) 0.5 (d) 0.25




1. Arrange the following steps in proper order to find the height of centre of gravity from the base of an equilateral triangular lamina.

(A) Centroid divides the median in the ratio 2 : 1, so divide the median in the ratio 2 : 1 and find the lengths of the two parts.

(B) Find the height of the median using Pythagoras theorem. (C) Divide the equilateral triangle into two right angle triangles by drawing

a median on its base. (D) Centre of gravity of an equilateral triangular lamina lies at its centroid. (E) The height of the centroid from the base gives the height of centre of

gravity from the base of the triangle. (a) BCDEA (b) DABCE (c) DBCEA (d) DCBAE

2. A crow bar of length 1.5 m is used to lift a load of 75 kg weight by placing the fulcrum at a distance of 20 cm from the load. Arrange the following steps in sequential order to find the effort (in N) applied on the crow bar to lift the load.

(A) Substitute the values in the law of levers, i.e, load × load arm = effort × effort arm.

(B) The distance between the load and the fulcrum is taken as load arm. (C) Convert the load into newton by multiplying with g and convert the

length of crow bar into cm. (D) By subtracting the load arm from the length of the crow bar, we will get

the length of effort arm.

(E) Determine the effort, i.e. Effort =×load load arm

effort arm

(a) CDABE (b) CADBE (c) CBDAE (d) ADCBE


Column A Column B

(A) Stream lining of bodies (a) Neutral equilibrium

(B) Centre of gravity of boomerang (b) Within the body

(C) A cylindrical vessel resting on a curved surface

(c) Friction is removed

(D) Centre of gravity of a solid right circular cone resting on its base

(d) Minimizes friction

(e) Outside the body

(f) Unstable equilibrium


Space for rough work (a) A → c; B → e; C → f; D → b (b) A → d; B → e; C → a; D → b (c) A → d; B → b; C → f; D → e (d) A → c; B → e; C → b; D → f

4. Assertion (A): Work done by a force acting on a body towards the centre of a circular path is zero.

Reason (R): The direction of force is perpendicular to its displacement. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

5. Assertion (A): When a person steps out of a boat, the boat moves backwards. Reason (R): The reaction force acting on the boat is in the opposite direction

to the direction of movement of the person. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

6. A force can produce an acceleration of 2 m s–2 and 6 m s–2 on bodies A and B, respectively, when applied individually. What is the acceleration produced (in m s–2), if the bodies are combined and the same force is applied?

(a) 1.0 (b) 1.5 (c) 3.0 (d) 6.0

7. Consider the Moon and an artificial satellite of earth. Weightlessness is experienced by a person _________.

(a) on the moon as well as in the artificial satellite. (b) only in the artificial satellite. (c) only on the moon. (d) neither on the moon nor in the artificial satellite.

8. What is the percentage change in the momentum of the body, if the mass of a body is doubled and its velocity is reduced by half?

(a) 0% (b) 10% (c) 50% (d) 100%

9. Two bodies A and B moving towards each other along a straight line, coa-lesce after collision. The system will move in the initial direction of A, if _________.

(a) the velocity of A is more than that of B before collision. (b) mass of A is more than that of B. (c) acceleration of A is more than that of B. (d) the momentum of A is more than that of B before collision.


Space for rough work 10. A body ‘A’ of mass 5 kg moving with velocity of 5 m s–1 collides with a body B initially at rest and bounces back along same line with a velocity of 2 m s–1. What is the force exerted on body B by A (in N), if the collision takes place for 0.1 milli second?

(a) 20 × 104 (b) 30 × 104

(c) 35 × 104 (d) 40 × 104

11. A body of mass 1 kg is accelerated from rest to 2 m s–1 in 1 s. Work done on it in 5 s is _______ joule.

(a) 50 (b) 8 (c) 0.4 (d) 10

12. A certain quantity of mercury is present in a cylindrical vessel of cross sec-tional area ‘A’ upto a height, h. The mercury is then transferred to another cylindrical vessel of cross sectional area 2A. What is the shift in the centre of gravity of mercury with respect to the base of the cylindrical vessels?

(a) h (b) h2

(c) h23

(d) h4

13. A spring balance is used to weigh an object of mass M kg hanged from the centre of a lever as shown in figure. What is the mass of the object (in kg), if the reading shown by the spring is 60 kg wt and the lever is in equilibrium? (g = 10 m s–2)

M

1.5 m

1m

(a) 100 (b) 200 (c) 150 (d) 175

14. If the efficiency of a pulley system having four pulleys is 80%, then calculate its mechanical advantage.

(a) 2.0 (b) 4.0 (c) 1.6 (d) 3.2


Space for rough work 15. A rectangular cuboid whose face ABCD shown with measurements in the figure is cut into two halves diagonally (along AC or BD) and the lower- half portion is used as an inclined plane. What is the mechanical advantage of the inclined plane formed?

D

C

5 cm

12 cm

B

A

(a) 335

(b) 225

(c) 235

(d) 523




1. Friction in parts of a machine can be reduced by using _____ . (a) iron filings (b) lubricants (c) ball bearings (d) both (b) and (c)

2. When a fast moving bus is stopped suddenly, the passengers sitting in it tend to fall forwards. This is due to _____ .

(a) inertia of rest. (b) inertia of motion. (c) inertia of direction. (d) inertia of speed

3. What is the work done to lift a body of mass 5 kg to a height of 50 m from the ground (in J)? (g = 10 m s–2)

(a) 250 (b) 2.5 × 1010

(c) 2.5 × 103 (d) 2.5 × 10–4

4. A machine is operated by an effort of 25 N and the effort has a downward displacement of 2.5 m in raising a load of weight 100 N through 10 cm. What is the efficiency of machine (in %)?

(a) 250 (b) 40 (c) 25 (d) 16

5. Forceps is an example of _____ order lever. (a) 1 (b) 2 (c) 3 (d) 1 or 2

6. 1 N of force is equal to _____ dyne. (a) 104 (b) 10–7 (c) 10–5 (d) 105

7. A constant force of 100 N acts on a body for 8 s for changing its momentum. What is the change of momentum of the body (in N)?

(a) 400 (b) 800 (c) 200 (d) 100

8. The power delivered by a machine if it lifts an object of mass 1000 kg to 4 m height in 1 minute is _____ kW.

(a) 0.7 (b) 466 (c) 666.6 (d) 66.66



Column A Column B

(P) Newton’s first law (p) F = ma

(Q) Newton’s second law (q) Recoil of a gun

(R) Newton’s third law (r) Law of inertia

(a) P → q; Q → r, R → p (b) p → P; Q → r, R → q (c) p → r; Q → p, R → q (d) P → q; Q → p; R → r

10. A car of mass 1500 kg moving at a speed of 90 km h–1 collides with another car at rest. After collision, both have a common velocity of 50 km h–1. The mass of the car which is initially at rest is _____ kg.

(a) 1100 (b) 1200 (c) 1300 (d) 1400

11. The physics teacher gave a rod of length ‘’ units to Ram and the teacher

asked Ram to find the shift in the C.G. when 15

of the total length of the rod

is removed. The answer of Ram will be ____units. (a) 0.4 (b) 0.2 (c) 0.8 (d) 0.1

12. A crow bar of length 1.14 m is used to move a block of mass 100 kg wt. If the effort arm is 100 cm when it is used as I-order lever, then the minimum effort required to move the block is _____ milli dyne. (Take g = 10 m s–2)

(a) 1.4 × 1010 (b) 1.4 × 108

(c) 140 (d) 1.4 × 105

13. A system of pulleys is used to lift a load of 500 kg wt. If the velocity ratio and M.A. are 0.9 and 5, then the efficiency and effort required to lift the load are ____ and _____, respectively.

(a) 5.6, 108 N (b) 5.6, 108 dyne (c) 2.6, 107 N (d) 2.6, 107 dyne

14. A car moving at 54 km h–1 is to be stopped by applying brakes in the next 5 m. If the car weights 1800 kg wt, then the net external force acting on it is ––––– .

(a) 4 × 109 N (b) 40 N (c) 4 × 104 dyne (d) 4 × 104 N


Space for rough work 15. Write the steps in sequential order to determine the difference in the height of C.G. of a solid right circular cone of height 40 cm resting on its base and a solid cylinder of length 1 m and diameter 30 cm resting on its lateral surface.

(A) Find the difference between the height of C.G. from the base. (B) Determine the height of the C.G. from the base. (C) Note down the height of the solid cone and the diameter of the sphere. (a) ABC (b) BCA (c) ACB (d) CBA




1. Frictional force in a machine can be reduced by _____ . (a) using iron filings (b) lubricants (c) converting sliding motion into rolling motion (d) both (b) and (c)

2. Inertia is measured by _____ of the body. (a) momentum (b) mass (c) volume (d) density

3. If the work done to move a body of mass 6 kg to a height h is 4.8 × 109 erg, then h = _____ m. (take g = 10 m s–2)

(a) 8 (b) 8 × 102

(c) 8 × 105 (d) 8 × 107

4. A machine is operated with an effort of 50 N in raising a load of weight (W). What is the load, if the mechanical advantage is 2?

(a) 500 dyne (b) 5 N (c) 100 N (d) 5 dyne

5. The human hand is a III-order lever because _____ lies between fulcrum and _____ .

(a) effort, elbow (b) effort, load (c) load, effort (d) elbow, effort

6. The unit of impulse is same as the unit of ––––– . (a) weight (b) force (c) momentum (d) work

7. If the change in momentum of a body is 400 N s, then constant force applied on the body for 10 s is _____ kilo dyne.

(a) 40 (b) 40 × 102

(c) 40 × 103 (d) 4 × 102


Space for rough work 8. If the power delivered by a machine if it lifts an object of mass 2000 kg to 6 m height is 2000 W. Then, time taken by the machine is _____ min. (g = 10 m s–2)

(a) 1 (b) 2 (c) 3 (d) 4

9. Match the entries of Column A with those of Column B.

Column A Column B

(P) Balanced force (p) An apple falling down

(Q) Unbalanced force (q) Friction

(R) Contact force (r) A book resting on the table

(a) P → q; Q → p; R → r (b) P → p; Q → q; R → r (c) P → r; Q → q; R → p (d) P → r; Q → p; R → q

10. A car of mass 1200 kg moving at a speed of 72 km h–1 collides with another car of mass 1500 kg which is at rest. What is the common velocity of the two cars, if they move together after the collision (m s–1)?

(a) 32.04 (b) 3.204 (c) 8.9 (d) 89

11. The shift in the C.G. of a rod is 5 cm when 14

of the rod is removed. The original length of the rod is _____ m.

(a) 0.75 (b) 0.125 (c) 0.4 (d) 40

12. A system of pulleys is used to lift a load of 1000 kg wt. If the velocity ratio and the efficiency are 20 and 90%, respectively, then the effort required to lift the load is ____ N.

(a) 5.6 ×107 (b) 5.6 × 10–3 (c) 5.6 × 105 (d) 560

13. A crow bar of length 120 cm is used to move a block of weight 1000 N. If the load arm is 30 cm when it is used as a II-order lever with maximum mechan-ical advantage, then the minimum effort required is _____ N.

(a) 2.5 × 107 (b) 4 (c) 250 (d) 2.5 × 10–3

14. A car moving at 40 km h–1 is to be stopped by applying brakes in the next 4.0 m. If the average resultant force on it is 3.1 × 104 N, then mass of the car is _____ kg.

(a) 2009 (b) 2500 (c) 1500 (d) 1600

2.14 Answer Keys

Space for rough work 15. A brick of dimensions 12 cm × 6 cm × 3 cm is resting on its larger area and a cylinder of length ‘’ is resting on its circular plane area. Arrange the following steps in the correct sequence to determine the value of ‘’ if the difference in the height of center of gravity is 15.5 cm.

(A) Find the center of gravity of the brick and cylinder. (B) Note the dimensions of the brick and the difference in the height of

center of gravity. (C) Find the value of difference in the height of center of gravity. (D) Equate it with the given value and find . (a) BACD (b) ACBD (c) BCAD (c) BDAC

Answer Keys

Assessment Test I 1. (a) 2. (a) 3. (c) 4. (a) 5. (d) 6. (d) 7. (a) 8. (a) 9. (b) 10. (b) 11. (b) 12. (c) 13. (a) 14. (a) 15. (b)

Assessment Test II 1. (d) 2. (c) 3. (b) 4. (a) 5. (a) 6. (b) 7. (b) 8. (a) 9. (d) 10. (c) 11. (a) 12. (d) 13. (a) 14. (d) 15. (c)

Assessment Test III 1. (d) 2. (b) 3. (c) 4. (d) 5. (c) 6. (d) 7. (b) 8. (a) 9. (c) 10. (b) 11. (d) 12. (a) 13. (b) 14. (d) 15. (d)

Assessment Test IV 1. (d) 2. (b) 3. (a) 4. (c) 5. (b) 6. (c) 7. (b) 8. (a) 9. (d) 10. (c) 11. (c) 12. (d) 13. (c) 14. (a) 15. (a)



1. Assertion(A): It is not possible to take directly a person on the surface of the Moon.

Reason(R): Sound waves are mechanical waves. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

2. Match the statements of Column A with those of Column B

Column A Column B

(A) Mechanical wave (p) Crests and troughs

(B) Non mechanical wave (q) Compressions and rarefactions

(C) Longitudinal wave (r) Light

(D) Transverse wave (s) Ripples

(a) A → s; B → r; C → p; D → q (b) A → s; B → r; C → q; D → p (c) A → r; B → s; C → p; D → q (d) A → p; B → r; C → q; D → s

3. Arrange the following incidents in the decreasing order of time taken. (A) The sound produced under a liquid at a depth of 100 m to reach the

surface of liquid if the velocity of sound in the given liquid is 1500 m s–1. (B) A wave of frequency 100 Hz and wave length 2 m to travel through a

distance of 50 m. (C) A seconds pendulum to complete 50 oscillations. (D) Light to reach on the surface of earth from the sun. [Distance between

the sun and the earth is approximately 1496 × 105 km]. (a) CDBA (b) ABCD (c) ACBD (d) DCBA



Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Wave Motion and Sound; Page number - 5.1–5.12

Chapter 3 Wave Motion and Sound 3.2

Space for rough work 4. Time period of a pendulum changes _________ (A) when the work done to oscillate the pendulum is changed. (B) when the bob is immersed in water. (C) when the mass of the bob is increased. (D) when weight of the pendulum is increased without changing its mass. (a) B, C and D (b) B and D (c) A, B, C and D (d) A, B and D

5. Sound produced by a tuning fork travels from air to glass. Which of the fol-lowing physical quantities remains the same?

(a) Velocity (b) Frequency (c) Wavelength (d) Amplitude

6. If V1 and V2 are the velocities of sound in solid and liquid, respectively, then VV

1

2

.

(a) ≤ 1 (b) >1 (c) <1 (d) =1

7. The time period of a pendulum of length ‘’ and mass of the bob ‘m’ is T. The time period of a pendulum with mass of the bob 2m and length is _________.

(a) T (b) 2T (c) 3T (d) 4T

8. When a simple pendulum oscillates with a small amplitude ‘a’, its time period is T. What is its time period, when it oscillates with a small amplitude 2a?

(a) T (b) 2T (c) 4T (d) 8T

9. If the velocity of a wave is 200 m s–1 and the time period of its source is 0.001 s, then its wave length is _________.

(a) 2 m (b) 20 cm (c) 2 cm (d) 2 mm

10. The frequency of vibration of a pendulum is ‘n’. What is its time period, if the length of the pendulum is doubled?

(a) 2 n (b) n2

(c) n2

(d) n2


Space for rough work 11. The displacement time graph of a simple pendulum is shown below. Calcu-late its frequency in Hz.

Time(s)1

(d

isp

lace

men

t)

0 3

2

20 cm

4

(a) 0.01 (b) 2 (c) 0.3 (d) 0.25

12. Which of the following statements is incorrect? (a) Sound requires a material medium to travel. (b) Sound waves are mechanical waves. (c) Sound waves are produced by vibrating bodies. (d) Sound waves have the maximum velocity among all the waves.

13. Sound of a thunder is heard ‘t’ s after the flash of lightning is seen. Determine the distance of the cloud from the ground if velocity of sound is v m s–1. [Neglect the time taken for the light to travel]

(a) vt

(b) vt (c) tv

(d) v + t

14. The frequencies of two tuning forks A and B are 200 Hz and 100 Hz, respectively. What is the ratio of the velocity of sound, when the sound is propagated through a given medium?

(a) 2 : 1 (b) 1 : 2 (c) 1 : 1 (d) 4 : 1

15. If length of a pendulum of time period T is doubled, its frequency is _________ .

(a) 12T

(b) 1T

(c) 2T (d) 2T




1. Assertion(A): A person standing at equal distances from a source of sound which is placed in water and another source which is placed in air. If sound is produced by both the sources, the sound produced in the water is heard first.

Reason(R): The speed of sound in liquid is more than that in gases. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.


Column A Column B

(A) Velocity of a wave (p) Velocity × Time period

(B) Frequency of a wave(q) Number of waves

time taken

(C) Wave length (r) Depends on source

(D) Frequency (s) Depends on medium

(a) A → p; B → q; C → s; D → r (b) A → s; B → r; C → q; D → p (c) A → r; B → s; C → p; D → q (d) A → s; B → r; C → p; D → q

3. Arrange the following incidents in the increasing order of frequency of occurrence.

(A) Oscillations of a seconds pendulum. (B) Rotation of the Earth in its own axis. (C) Sound waves produced in air from a siren. [Given velocity of sound

through air 340 m s–1 and wave length is 2 cm]. (D) Waves to reach the sea shore. [Given time interval between two waves

to reach the sea shore is 10 s]. (a) ABDC (b) DBAC (c) BDAC (D) CBDA

4. Frequency of oscillation of a pendulum changes with _________. (A) time period (B) amplitude (C) length of the pendulum (D) mass of the bob (a) A and C (b) A, C and D (c) B and C (d) B, A and C


Space for rough work 5. As the sound propagates through a medium, its _________ changes. (a) velocity (b) wavelength (c) frequency (d) amplitude

6. Sound produced by a tuning fork travels through a solid and liquid media. If f1 and f2 are the frequencies of sound in solid and liquid, then find the

value of ff1

2

.

(a) =1 (b) >1 (c) ≥1 (d) <1

7. What is the new time period of a pendulum, if the length of a pendulum of time period T is doubled?

(a) T2 (b) T2 (c) 2T2 (d) 4T

8. If a pendulum makes 2 oscillations per second, its time period is _________ s. (a) 2 (b) 5 (c) 0.2 (d) 0.5

9. If the velocity of sound wave 330 m s–1 and the frequency of oscillations is 10 Hz, then the distance between an adjacent compression and rarefaction is _________ m.

(a) 33 (b) 16.5 (c) 66 (d) 44

10. What is the time period a body, if the frequency of a body is equal to the minimum value of the audible range of frequency?

(a) 0.05 (b) 0.5 (c) 0.2 (d) 2

11. From the graph shown below, determine the amplitude of oscillation.

Time(s)1

(dis

pla

cem

ent)

0 3

2

20 cm

4

(a) 80 cm (b) 40 cm (c) 20 cm (d) 10 cm

12. To increase the frequency of oscillation of a pendulum, its _________ (a) length should be increased. (b) length should be decreased. (c) time period should be increased. (d) amplitude should be increased.


Space for rough work 13. Sound cannot travel through _________. (a) solid (b) liquid (c) gas (d) vacuum

14. The time taken to complete 100 waves is 50 s. The frequency of the wave is _________ Hz.

(a) 1 (b) 2 (c) 0.5 (d) 5

15. Sound produced by a source travels through two different media. If the ratio of the velocity of sound waves travelling through the media is 1 : 3, then ratio of the wavelength is _________.

(a) 1 : 3 (b) 3 : 1 (c) 6 : 5 (d) 9 : 1




1. Write down the steps to verify the third law of simple pendulum in a proper sequence.

(A) Arrange a pendulum and determine its length. (B) Set the pendulum into oscillation and determine the time taken for 20

oscillations. (C) Determine the time period of oscillation (T) and find its square (T2). (D) Change the length of simple pendulum and repeat the experiment.

(E) Note the value of T2

in each case.

(a) CDBAE (b) ABCDE (c) CDABE (d) ABCED

2. If the distance between two successive troughs is 20 cm, then the distance between one of the crests to next trough is _______.

(a) 10 cm (b) 20 cm (c) 40 cm (d) 50 cm

3. An example for flute type instrument is _______ (a) clarinet (b) piccolo (c) oboe (d) bassoon


Column A Column B

(A) Loudness (a) Group of wave length

(B) Pitch (b) Single wave length

(C) High quality (c) Amplitude

(D) Low quality (d) Frequency

(a) A → c; B → d; C → b; D → a (b) A → c; B → d; C → a; D → b (c) A → d; B → c; C → b; D → a (d) A → d; B → c; C → a; D → b

5. Two persons are talking behind the wall. We can differentiate their voices by _______ even if their pitch and amplitude are equal.

(a) loudness (b) quality (c) timbre (d) Both (b) and (c)


Space for rough work 6. The oscillation of a simple pendulum is graphically represented as shown in figure. The frequency of the simple pendulum is _______ Hz.

2 4

6 cm

(a) 4 (b) 0.5 (c) 0.25 (d) 16

7. A wave of time period of 20 ms travels with a velocity of 2 m s–1. If the time period of another wave is 5 ms, then velocity of second wave and the ratio of their velocity are (wave length of the two waves is same) _______ and _______, respectively.

(a) 0.8 m s–1, 72

(b) 0.25 m s–1, 52

(c) 8 m s–1,14

(d) None of these

8. A sound wave is traveling from air to water. The velocity of the sound waves in air is 340 m s–1 and wavelength is 2 m. If the wave length of the sound wave in water is 1050 cm, then its velocity of wave in water is _______.

(a) 1785 m s–1 (b) 1.785 cm s–1

(c) 1.785 pm s–1 (d) 1585 m s–1

9. When a string fixed between two ends is plucked, a wave propagates along the string and reflects at the other end. If the velocity and frequency of the wave is 330 m s–1 and 1200 Hz, then the distance of first node and first anti-node from the fixed end of the string are _______ and _______, respectively.

(a) 0.1375 m, 0.6875 m (b) 0.138 m, 0.6 cm (c) 0.1375 m, 0.06875 m (d) None of these

10. If the length of a seconds pendulum is first decreased by 10 cm and its time period is measured and then increased by 15 cm and the time period is measured, then the ratio of the time periods in two cases is _________. (Take g = 9.8 m s–2)

(a) 6 : 7 (b) 6 : 7

(c) 42 : 1 (d) 6 : 7


Space for rough work 11. When you speak to your friend, which of the following parameters has a unique value in the sound produced?

(a) frequency (b) velocity (c) amplitude (d) wavelength

12. The time period of a pendulum on the surface of a planet is 8 s and same simple pendulum is a seconds pendulum on the Earth surface. What is the

value of x, if the acceleration due to gravity of the planet is x1 times of that

of the earth? (a) 16 (b) 8 (c) 4 (d) 2

13. The velocity of sound increases by 50% when it enters a liquid from air and when it enters another liquid from air, increase in velocity is 150%. What is the ratio of % increase in the wavelength in two cases?

(a) 1 : 1 (b) 1 : 2 (c) 1 : 4 (d) 1 : 3

14. The length of a seconds pendulum on the Earth to be decreased to make it as a seconds pendulum on the surface of the Moon is _________ times its length on the Earth.

(a) 16

(b) 116

(c) 56

(d) 76

15. Two sound waves ‘P’ and ‘Q’ travel with amplitude 3 mm and 4 mm. What is the ratio of their loudness?

(a) 3 : 2 (b) 9 : 16 (c) 2 : 3 (d) 16 : 9




1. The time taken by a particle to move from one extreme position to the other extreme position is 0.1 s. If the distance between two adjacent crests is 1.5 m, write the steps in sequential order to determine the velocity of the wave.

(A) Note down the wavelength (λ). (B) Find the frequency (f). (C) Note down the time period (T). (D) Find the velocity by the formula v = f λ (a ) BCAD (b) CBAD (c) ABCD (d) ACBD

2. What is the wavelength, if the distance between one crest to the next trough of a wave is 12.5 cm?

(a) 25 m (b) 25 cm (c) 2.5 m (d) None of these

3. The musical instrument in which a membrane is excited to produce musical notes is called _________ instrument.

(a) flute type (b) reed type (c) stringed (d) percussion


Column A Column B

(A) Pitch (a) Hertz

(B) Wavelength (b) Centimetre

(C) Loudness (c) No unit

(D) Amplitude (d) Decibel

(a) A → c; B → b; C → d; D → b (b) A → a; B → b; C → d; D → b (c) A → c; B → d; C → b; D → a (d) A → c; B → d; C → a; D → b

5. If the loudness of sound of two persons is equal, then _________. (a) Their frequency of sound is equal (b) Their amplitude of sound is equal (c) Their quality of sound is equal (d) Both (a) and (b)


Space for rough work 6. The frequency and amplitude of simple pendulum are 2 Hz and 4 cm, respectively. What is the suitable graph for this simple pendulum?

(a)

X

time

0.2 s

2 cm

Y Amplitude

(b)

X 0.5 s

4 cm

Y

time

Amplitude

(c)

2 s

4 cm

Y

time

Amplitude

X

(d)

0.5 s 4 cm

Y

X

time

Amplitude

7. A wave of frequency 100 Hz travels with a velocity of 3 m s–1. If the time period of another wave is 8 ms, then its velocity and also the ratio of their velocities are _________. (Assume that the wavelength of the two waves is the same).

(a) 308

m s–1, 52

(b) 308

m s–1, 45

(c) 308

m s–1, 25

(d) None of these

8. A sound wave travels from air to glass. The velocity of sound in air is Va and the wavelength is λa. What is the velocity in glass, if the wave length of the sound wave in the glass is λg?

(a) v

va g

a

λ (b)

vg a

a

λ

λ

(c) v

va a

g

λ (d)

va a

g

λλ

9. When a string fixed between two ends is plucked, a wave propagates along the string and reflects at the other end. If the frequency and distance of the first anti-node from the first end of the string are 1000 Hz and 2 m, respec-tively, the velocity of the wave is _________.

(a) 8000 m s–1 (b) 8000 cm s–1

(c) 8 × 10–3 cm s–1 (d) 9000 m s–1

10. The length of a seconds pendulum is first decreased by 10 cm and its time period is found, then increased by x cm and its time period is found. If the ratio of time periods in two cases is 3 : 2, then find the value of x

(a) 10 (b) 20 (c) 30 (d) 40


Space for rough work 11. When a sound wave is traveling from one medium to another medium, which of the following parameters have a unique value in the sound propagation?

(a) Frequency (b) Wavelength (c) Velocity (d) Speed

12. The time period of a simple pendulum is 4 s on the surface of the earth. What is the length of the pendulum (in m), if it takes 2.3 s to complete one oscillation on the surface of the planet whose ‘g’ value is thrice that of the earth? (Take π2 = g)

(a) 1 (b) 2 (c) 3 (d) 4

13. The velocity of sound increases by 75% when it enters into a liquid from air and there is a 25% increase in the wavelength when it enters into another liquid from the first liquid. The velocity of sound in the second liquid is _________ if the velocity of sound in 1st liquid is 1100 m s–1.

(a) 1,275 m s–1 (b) 1,375 m s–1

(c) 1,375 cm s–1 (d) 1,275 cm s–1

14. The time period of a simple pendulum on surface of the Earth is 5 s. To maintain the same time period on the surface of the planet of g value twice that of the earth, the change in the length of the pendulum is _________. (Take the value of acceleration due to gravity on the Earth as π2)

(a) 6.25 m (b) 6.25 cm (c) 62.5 nm (d) 62.5 pm

15. The % increase in the amplitude of sound is 20%, then % change in loudness is _________.

(a) 11 (b) 22 (c) 33 (d) 44

Answer KeysAssessment Test I

1. (a) 2. (b) 3. (d) 4. (b) 5. (b) 6. (b) 7. (a) 8. (a) 9. (b) 10. (b) 11. (d) 12. (d) 13. (b) 14. (c) 15. (a)

Assessment Test II 1. (a) 2. (d) 3. (c) 4. (d) 5. (d) 6. (a) 7. (b) 8. (d) 9. (b) 10. (a) 11. (c) 12. (b) 13. (d) 14. (b) 15. (a)

Assessment Test III 1. (b) 2. (a) 3. (b) 4. (a) 5. (b) 6. (c) 7. (c) 8. (a) 9. (c) 10. (d) 11. (b) 12. (a) 13. (d) 14. (c) 15. (b)

Assessment Test IV 1. (d) 2. (b) 3. (d) 4. (a) 5. (b) 6. (b) 7. (b) 8. (b) 9. (a) 10. (c) 11. (a) 12. (d) 13. (b) 14. (a) 15. (d)



1. What will happen when heat energy flows from one body to another? (a) There is always a change in temperature. (b) There is always a physical contact between two bodies. (c) There is always a change in state of the substance. (d) There is no change at all.

2. Temperatures of three bodies A, B and C are 20° C, 20 K and 20° F, respec-tively. Which among them has the highest temperature?

(a) A (b) B (c) C (d) All of them have the same temperature

3. The normal human body temperature is 98.4° F. If the body temperature of a person is 313 K, then the person ____________.

(a) has normal temperature. (b) high fever. (c) has temperature less than normal temperature. (d) nothing can be said about his health condition.

4. A piece of ice is floating in water. The temperature of both water and ice is 0° C. What will happen when the surrounding temperature is –5° C?

(a) the quantity of ice increases. (b) the quantity of water increases. (c) the quantity of water and ice remains the same. (d) the quantity of water and ice increases.

5. If 1000 cal of heat energy is supplied to water at 30° C, then ____________. (a) water starts to boil. (b) water completely converts to steam.


Heat

Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Heat; Page number - 6.1–6.17

Chapter 4 Heat 4.2

Space for rough work (c) it will either remain in liquid state or converts to steam depending on its mass.

(d) quantity of water in the container will decrease.

6. 1000 cal of heat energy is supplied to a body ‘X’ and 2000 cal of heat energy is supplied to body ‘Y’ and they are kept in contact. Then

(a) the heat energy flows from Y to X. (b) the heat energy flows from X to Y. (c) the heat energy may flow from X to Y or Y to X depending upon their

specific heat capacity. (d) the heat energy may flow from X to Y or Y to X depending upon their

temperature.


Column A Column B

(A) Temperature (a) form of energy

(B) Heat (b) depends on mass

(C) Specific heat (c) does not depend on mass

(D) Heat capacity (d) degree of hotness

(a) DACB (b) ACBD (c) ACDB (d) BCDA

8. What is the specific heat capacity of water? (a) 1 cal g–1°C–1

(b) 4186 J g–1°C–1

(c) 4186 kJ g–1°C–1

(d) 0.04186 J g–1°C–1

9. Which of the following plays an important role when water is used as a coolant?

(a) Specific heat capacity (b) Melting point (c) Boiling point (d) Density

10. The length of a mercury column in a thermometer at the melting point of ice is 2 cm and at the boiling point of water it is 10 cm. What is the temperature of a body if the mercury thread is at 5 cm?

(a) 25° C (b) 30° C (c) 50° C (d) 60° C

11. Assertion (A): Cooking becomes difficult on the top of a mountain. Reason (R): At higher altitude the pressure is less, and hence, the boiling

point of water decreases with altitude.


Space for rough work (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

12. Assertion (A): The sea and land breezes are formed due to convection cur-rent of air.

Reason: During the day time, sea water gets heated faster than land. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

13. Choose the correct statement. (A) Two pieces of ice can be joined to form a single piece by pressing them

with high pressure. (B) As the pressure increases the melting point of ice decreases. (a) Only (A) is correct (b) Only (B) is correct (c) Both (A) and (B) are correct (d) Both (A) and (B) are incorrect

14. Arrange the following substance in the increasing order of their specific heat capacities.

(A) 100 cal heat is required to change the temperature of 10 g of a substance from 10°C to 20° C.

(B) 200 cal heat is required to change the temperature of 5 g of a substance 200 K to 230 K.

(C) 420 joule of heat is required to change the temperature of a substance of mass 50 g from 0°C to 5° C.

(a) ABC (b) BCA (c) ACB (d) CBA

15. Which among the following physical quantities is expressed in erg g–1? (a) Specific heat capacity (b) Heat capacity (c) Heat energy (d) Specific latent heat

Chapter 4 Heat 4.4



1. When does the temperature of a body change? (a) only when a body absorbs heat. (b) only when a body is kept in contact with another body at a lower

temperature. (c) only when a body is heated in a heating device. (d) None of these

2. The temperature of three bodies A, B and C are increased by 1°C, 1°F and 1 K, respectively. What will be the relation between these temperatures, if these change in temperature are represented by ΔC, ΔF and ΔK, respectively?

(a) Δ C = Δ F = Δ K (b) Δ C = Δ K > Δ F (c) Δ F > Δ C > Δ K (d) Δ F = Δ C > Δ K

3. The temperature of a body ‘A’ is 60°C and the temperature of a body ‘B’ is 122°F. What will happen when they are in contact with each other?

(a) The heat flows from A to B (b) The heat flows from B to A (c) They are in thermal equilibrium (d) Heat flows from A to B or B to A depending upon the surrounding

temperature.

4. A body at 110°C is dropped into water at 100°C. What happens to the quan-tity of water in the container?

(a) remains the same (b) increases (c) decreases (d) the body converts to the liquid state

5. 1000 cal of heat energy is supplied to 100 g of ice at 0° C. What is the final temperature of the content?

(a) 0° C (b) 20° C (c) 5° C (d) 3° C

6. What will happen to a body in its solid state, when it is dropped into its liquid form (neglect the flow of heat to the surroundings)?

(a) the body melts (b) the liquid form converts to its solid state (c) no changes takes place (d) either (a) or (c) depending upon their temperature



Column A Column B

(A) Absolute scale of temperature

(a) Expansion on heating

(B) Bimetallic strip (b) Kelvin

(C) Radiation (c) No medium is required

(D) Convection (d) Medium is required

(a) BCAD (b) BACD (c) ACBD (d) DBCA

8. Arrange the following processes in the increasing order of time taken. In all the following processes, a similar heating device is used.

(A) 10 g of ice is just melted. (B) 10 g of water at its boiling point is just converted to steam. (C) 10 g of water at 0° C is boiled. (a) ABC (b) ACB (c) CBA (d) BCA

9. Which of the following properties plays an important role when water is used for fermentation?

(a) Specific heat capacity (b) Density (c) Boiling point (d) Melting point

10. The length of the mercury thread in a thermometer at 100° C and 50° C is 10 cm and 4 cm, respectively. What is the length of the mercury thread when it is kept in contact with melting ice?

(a) 0 (b) 2 cm (c) 1 cm (d) 3 cm

11. Assertion: If the humidity is high, the chance of rainfall is high. Reason: If humidity is high, water vapour will condense to form rain. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

12. Assertion: As we move away from the surface of the Earth in the atmosphere, the temperature increases.

Reason: As we move away from the surface of the Earth, we are more close to the Sun.


Chapter 4 Heat 4.6

Space for rough work 13. Choose the correct statement. (A) The melting point of all substances decreases with increase in pressure (B) The boiling point of water increases with the addition of impurities (a) Only (A) is correct (b) Only (B) is correct (c) Both (A) and (B) are correct (d) Both (A) and (B) are incorrect

14. Arrange the following substances in the increasing order of their heat capacity.

Substance MassInitial

temperatureFinal

temperatureHeat energy

absorbed

a 10 g 5° C 10° C 100 cal

b 20 g 20° C 50° C 200 cal

c 30 g 40° C 50° C 400 cal

(a) ABC (b) BAC (c) CAB (d) ACB

15. Which among the following physical quantities is expressed in erg°C–1? (a) Specific heat capacity (b) Heat capacity (c) Specific latent heat (d) Heat energy




1. Thermal capacity of a given substance depends on its ____________. (a) specific heat capacity (b) volume (c) temperature (d) mass


Column A Column B

(A) Melting point of wax (p) 0.5 cal g–1°C–1

(B) Absolute zero temperature (q) 60°C

(C) Specific heat capacity of ice (r) 4200 J kg°C–1

(D) Specific heat capacity of water (s) –273°C

(a) A → q; B → s; C → r; D → p (b) A → q; B → r; C → p; D → s (c) A → q; B → s; C → p; D → r (d) A → q; B → r; C → s; D → p

3. Which of the following has more energy? (a) Water at 100° C (b) Steam at 100° C (c) Oil at 100° C (d) Both (a) and (b)

4. ‘A medium is necessary for the transmission of heat’. Which of the following is related to the given statement?

(a) Conduction (b) Convection (c) Radiation (d) Both (a) and (b)

5. Choose the one from the following where less thermal transmission takes place.

(a) White and rough surface (b) White and smooth surface (c) Smooth and black surface (d) Black and rough surface

6. 15 g of water at 100° C is mixed with 15 g of ice at 0° C. What is the temperature of the mixture?

(a) 50° C (b) 66.6° C (c) 10° C (d) 61.3° C

Chapter 4 Heat 4.8

Space for rough work 7. Choose the correct one from the following:

(a) The rate of conduction of heat depends upon the nature of the medium.

(b) When the room temperature is raised, then a pendulum clock loses time.

(c) The heat supplied during change of state at constant temperature is called latent heat.

(d) All of the above.

8. Arrange the following steps in proper sequence for the construction and calibration of Fahrenheit thermometer.

(P) The distance between the two fixed points is called fundamental interval. It is divided into 180 equal divisions in Fahrenheit scale.

(Q) Take a thick walled capillary tube with thin walled glass bulb and fill it with mercury with the help of a funnel.

(R) Mark the upper fixed point with the help of hypsometer.

(S) Place the glass bulb in a hot oil bath while filling the mercury to remove the air bubbles.

(T) Lower fixed point is marked by immersing the bulb of the thermometer in melting ice taken in a funnel.

(a) SRTPQ (b) QSRPT (c) QSRTP (d) QRSTP

9. Two identical metallic balls of temperature 20° C and 80° C are kept in contact with each other. Then the ratio of heat lost by one ball to heat gained by another ball?

(a) 2 : 1 (b) 3 : 2 (c) 1 : 1 (d) 2 : 3

10. The ratio of Fahrenheit reading to Celsius reading is 3. What is the reading on Celsius scale?

(a) 403

C (b) 203

C

(c) 803

C (d) None of these

11. Specific latent heat of ice is _________.

(a) 336 J g–1

(b) 3,36,000 J kg–1

(c) 80 cal g–1

(d) All of the above


Space for rough work 12. A 200 W water heater is used to heat 1000 g of water. The heater is switched ON for 4.2 minutes and the initial temperature of water is 35°C, then the final temperature of water is _________.

(a) 40° C (b) 45° C (c) 70° C (d) 47° C

13. What will be the amount of mercury, if the specific heat capacity of mercury is 0.14 J g–1°C–1 and heat capacity is 140 J g–1°C–1?

(a) 1 kg (b) 100 g (c) 10 g (d) 200 g

14. An immersion heater of power 20 W just keeps 200 g of solid metal at its melting point. The heater is switched ON and temperature starts raising after 4 min, then the specific latent heat of fusion of the metal is _________.

(a) 24 J g–1 (b) 24 cal g–1

(c) 24 cal kg–1 (d) 24 J kg–1

15. A body at the temperature T1 is mixed with another body of equal mass at the temperature T2 and both have the same heat capacity. If T1 > T2, then the rise in temperature of the cold body is equal to the fall in temperature of the hot body. What is the final temperature of mixture?

(a) zero (b) T T1 2

2+

(c) T T1 2

2− (d) T1 – T2

Chapter 4 Heat 4.10



1. Specific heat capacity of a given substance is independent of _________. (a) mass (b) temperature (c) volume (d) All of these


Column A Column B

(A) Bimetallic strip (p) J kg–1

(B) Clinical thermometer(q) Unequal expansion of

metals

(C) S.I unit of latent heat of vapourization (r) J K–1

(D) SI unit of heat capacity(s) Cannot measure boil-

ing point of water

(a) A → q; B → s; C → r; D → p (b) A → q; B → s; C → p; D → r (c) A → q; B → r; C → p; D → s (d) A → q; B → p; C → r; D → s

3. Which of the following has less energy? (a) A substance at absolute zero temperature (b) Water at 0° C (c) Ice at 0° C (d) Both (b) and (c)

4. A medium is not required for the transmission of heat. Choose the correct one from the following which is related to above statement.

(a) Radiation (b) Conduction (c) Convection (d) All of the above

5. Choose a good radiator of thermal energy from the following: (a) Black surface (b) Green-coloured surface (c) White surface (d) Yellow-coloured surface

6. 10 g of water at 60°C is mixed with 15 g of water at t1. If the temperature of the mixture is 40°C, then the value of t1 is _________.

(a) 13.3° C (b) 13° C (c) 26° C (d) 26.6° C


Space for rough work 7. Choose the incorrect one from the following:

(a) ∆C F K180 180 100

=∆

=∆

(b) Under normal conditions, naphthalene undergoes sublimation. (c) When pressure is increased, then the boiling point of the substance

increases. (d) Boiling point of water is 100° C at normal atmospheric pressure.

8. Write the following statements in the sequential order to find the amount of heat required to convert 50 g of ice at – 5° C into steam at 110° C.

(P) Further ice at 0° C is converted into water at 0°C by utilizing the amount of heat Q2 = Mwater Lfusion.

(Q) By consuming Q3 = mw Sw (100 – 0) of heat, the water at 0° C rises the temperature to 100°C

(R) Sum of Q1, Q2, Q3, Q4 and Q5, then we get the total quantity of heat required to convert 50 g of ice at – 5° C to steam at 110° C

(S) Calculate the amount of heat used to increase the temperature of ice upto 0°C

(T) Next, water at 100° C converts into steam at 100° C by taking the heat Q4 = mw Lv. Finally steam increases its temperature up to 110° C by tak-ing Q5 = mst sst (110 – 100) of heat.

(a) SPTQR (b) SPTRQ (c) SPQTR (d) SQPTR

9. What is the final temperature of the mixture, when the water at 10° C is mixed with same amount of water at 90° C?

(a) 45° C (b) 70° C (c) 40° C (d) 50° C

10. If the ratio of Celsius to Kelvin reading is 4, then the reading of Kelvin scale is _________.

(a) –91 K (b) 373 K (c) 91 K (d) 1092 K

11. Specific latent heat of steam is _________. (a) 2260 J g–1 (b) 540 cal g–1

(c) 226 × 104 J g–1 (d) both (a) and (c)

12. What is the power of a heater, if the heater is used to warm the water of 100 g mass from 20° C to 80° C for 2 min?

(a) 240 W (b) 210 W (c) 240 J (d) 420 J

4.12 Answer Keys

Space for rough work 13. The mass of copper is 0.120 kg. If the specific heat capacity is 100 cal g–1°C–1, then thermal capacity in SI unit is _________.

(a) 120 cal (b) 50.4 J (c) 12 J (d) 50.4 cal

14. The specific latent heat of fusion of ice is 80 cal g–1. An immersion heater of power 25 W is kept in 100 g of ice at its melting point. If the heater is switched ON, then the time after which the temperature of ice starts raising is _________.

(a) 320 min (b) 320 s (c) 8.3 min (d) 22.4 min

15. An equal amount of water is taken in two different containers and their tem-peratures are 90° C and 30° C, respectively. If the rise in temperature of the cold water is equal to the fall in temperature of the hot water, then common temperature of the mixture is _________.

(a) 45° C (b) 66° C (c) 30° C (d) 60° C


1. (d) 2. (a) 3. (b) 4. (a) 5. (c) 6. (d) 7. (a) 8. (a) 9. (a) 10. (a) 11. (a) 12. (c) 13. (b) 14. (d) 15. (d)

Assessment Test II 1. (d) 2. (b) 3. (a) 4. (c) 5. (a) 6. (d) 7. (b) 8. (d) 9. (a) 10. (b) 11. (a) 12. (d) 13. (b) 14. (b) 15. (b)

Assessment Test III 1. (d) 2. (c) 3. (b) 4. (d) 5. (b) 6. (c) 7. (d) 8. (c) 9. (c) 10. (c) 11. (d) 12. (d) 13. (a) 14. (a) 15. (b)

Assessment Test IV 1. (a) 2. (b) 3. (a) 4. (a) 5. (a) 6. (d) 7. (a) 8. (c) 9. (d) 10. (a) 11. (d) 12. (b) 13. (b) 14. (d) 15. (d)

5Light



1. A light ray incident on a reflecting surface with an angle of incident of 30°. The angle of deviation is _________.

(a) 60° (b) 30° (c) 120° (d) 90°

2. What is the nature of the image formed by a plane mirror? (a) real (b) magnified (c) virtual (d) diminished

3. What is the number of images formed, when the angle between two mirrors is 72°?

(a) 4 (b) 5 (c) 6 (d) 3

4. A light ray travelling from medium ‘A’ to medium ‘B’ undergoes refraction and another light ray travelling from ‘A’ to ‘C’ undergoes reflection. If A, B and C are transparent media and μA, μB and μC are their refractive indices, which of the following is necessarily true?

(a) μA > μB (b) μA < μB

(c) μB > μC (d) μA > μC

5. A light ray travels through three media A, B, and C as shown below. If vA, vB and vC are the velocities of light in A, B, C respectively, then

A

B

C

60°

45°

30°

(a) vB > vA (b) vB > vC

(c) vC > vA (d) vB = vC


Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Light; Page number - 7.1–7.47

Chapter 5 Light 5.2

Space for rough work 6. Assertion (A): When visible light is passed through a prism, violet colour is seen at the bottom of the screen.

Reason (R): Prism has the highest refractive index for violet light. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

7. Assertion (A): A convex lens placed in air always forms a real image. Reason (R): Any light ray passing through a convex lens is converged. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

8. Objects are placed in front of a convex lens of focal length 20 cm at the fol-lowing positions. Arrange these positions in the increasing order of the size of their image.

(A) At 2F1

(B) At F1

(C) Between 2F1 and F1

(D) Infinity (a) DACB (b) CADB (c) BACD (d) BCAD

9. A light ray travels from air to four different media as shown below. Arrange them in the increasing order of wave length of light rays in these media.

(A)

45°

30°

(B)

40°

30°

(C) 30°

35°

(D)

10°

30°

(a) ACBD (b) DBCA (c) BCDB (d) CBDB



Column A Column B

(A) Blue colour of sky (a) Total internal reflection

(B) Mirage (b) Scattering of light

(C) Twinkling of stars (c) Dispertion

(D) Formation of rainbow (d) Refraction

(a) A → b; B → a; C → d; D → c; (b) A → a; B → b; C → c; D → d; (c) A → b; B → c; C → b; D → a; (d) A → c; B → d; C → b; D → a;

11. Which of the following takes place in periscopes in which prisms are used. (a) refraction (b) total internal reflection (c) reflection (d) scattering

12. The velocities of light through media ‘A’ and ‘B’ are V and 2V, respectively. The value of sin C is _________ [where ‘C’ is the critical angle].

(a) 12

(b) 13

(c) 3 (d) 2

13. An object of height 5 cm is placed in front of a convex lens of focal length 20 cm at a distance of 30 cm. What is the height of the image (in cm)?

(a) 20 (b) 30 (c) 10 (d) 40

14. The focal length of a eye lens is f. What is the value of the diameter of the eye ball?

(a) f (b) 2f (c) 3f (d) f2

15. A glass slab of thickness 5 cm and refractive 3/2 is placed over a photo. The apparent shift in position of the photo is _________ cm.

(a) 7/3 (b) 5/3 (c) 5/2 (d) 5/4

Chapter 5 Light 5.4



1. When a light ray incident on a reflecting surface, the angle of deviation is found to be 90°. What is the value of the angle of reflection?

(a) 45° (b) 90° (c) 160° (d) 120°

2. Image formed on a convex mirror is _________. (A) real (B) magnified (C) virtual (D) diminished (a) both (A) and (B) (b) both (C) and (D) (c) both (B) and (C) (d) both (A) and (D)

3. The number of images formed by the combination of two mirrors is 9. What is the angle between the two mirrors?

(a) 36° (b) 40° (c) 90° (d) both (a) and (b)

4. When a light ray travels from a medium P to Q, it undergoes total internal reflection. Then, avoiding normal incidence _________

(a) any light ray travelling from P to Q undergoes reflection (b) any light ray travelling from Q to P undergoes reflection (c) any light ray travelling from Q to P undergoes refraction (d) None of these

5. A light ray travels from medium P to Q and R as shown below. If μP, μQ and μR are the refractive indices of the media P, Q and R, respectively, then find the relation between them.

P

Q

R•

(a) μP > μQ (b) μR < μQ

(c) μR > μP (d) μP > μQ

6. Assertion (A): Violet and red light entering from air, travelling same distances through a glass slab travel for same time interval.

Reason (R): Velocities of violet and red light travelling through glass slab are same.


Space for rough work (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

7. Assertion (A): A convex lens placed in air always forms virtual image. Reason (R): Any light ray passing through a concave lens is diverged. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

8. When an object is moved away from a convex mirror, what happens to the image?

(a) becomes smaller (b) moves closer to the focus (c) becomes inverted (d) Both (a) and (b)

9. A light ray travels from a medium ‘M’ to four different media as shown below. Arrange them in the increasing order of critical angle.

(a)

45°

30°

(b)

40°

30°

(c)

30°

50°

Chapter 5 Light 5.6

Space for rough work (d)

55°

30°

(a) ABCD (b) DCBA (c) CABD (d) DBAC


Column A Column B

(A) Optic fibre communication (a) Reflection

(B) Apparent depth of swimming pool (b) Scattering

(C) Formation of image by a plane mirror. (c) Total internal reflection

(D) Orange colour of the sky (d) Refraction

(a) A → c; B → a; C → d; D → b (b) A → b; B → c; C → d; D → a (c) A → c; B → d; C → a; D → b (d) A → b; B → d; C → c; D → a

11. The periscopes in which mirrors are used, _________ takes place (a) reflection (b) total internal reflection (c) refraction (d) scattering

12. The critical angle of a pair of media is ‘C’. If velocity of light through the denser medium is V, the velocity of the light through the rarer medium is _________.

(a) Sinc V2 (b) V

Sin C

(c) V

Sin C (d) V sin C

13. When an object of height 3 cm is placed in front of a convex lens of focal length 20 cm, the height of the real image is found to be 6 cm. What is the distance between the object and image?

(a) 20 (b) 30 (c) 10 (d) 40


Space for rough work 14. The focal length of the defective eye lens of a person is less than the diameter of the eye ball. Then the person is suffering from _________.

(a) short sightedness (b) long sightedness (c) defect in cornia nerves (d) defect in optial nerve

15. A bird is flying horizontally above a swimming pool at a distance of 30 m above the surface of water. If the refractive index of water is 4/3, the appar-ent shift in position of the bird’s image is _________.

(a) 10 m (b) 20 m (c) 15 m (d) 12 m

Chapter 5 Light 5.8



1. Choose the correct statement (s). (a) An object is visible only if the light is reflected from it. (b) Light is the only form of energy which causes the sensation of vision. (c) Formation of a shadow is due to the rectilinear propagation of light. (d) All of the above.

2. The point of intersection of reflected rays is _______. (a) a real object (b) a real image (c) a virtual image (d) a virtual object

3. An optical instrument is placed inside the box as shown below. The incident rays and emergent rays are also shown. The optical instrument could be _______.

(a) only a plane mirror (b) only a convex mirror (c) only a concave mirror (d) both plane mirror and convex mirror

4. Light rays are incident on a plane mirror as shown below. What is the image distance with proper sign convention?

20 cm

(a) +20 cm (b) –20 cm (c) +40 cm (d) –40 cm

5. A concave mirror of focal length 30 cm forms a real image whose size is thrice the size of the object which is at the distance of _______ cm.

(a) 60 (b) 50 (c) 40 (d) 70

6. What should be the shift in the position of a plane mirror so that the shift in position of the image is 20 cm towards the mirror?

(a) 20 cm (b) 40 cm (c) 10 cm (d) 80 cm


Space for rough work 7. The velocity of light in air is 3 × 108 m s–1. What is the velocity of light in a medium whose refractive index is 1.8?

(a) 1.6 × 108 m s–1 (b) 1.32 × 108 m s–1

(c) 2.2 × 108 m s–1 (d) 2.8 × 108 m s–1

8. When a person suffering from long-sightedness looks at an object very close to him, the image distance of the eye lens is _______ that of a normal eye.

(a) lesser than (b) equal to (c) greater than (d) half of

9. In the outer space, the sky appears _______. (a) blue due to scattering (b) orange due to refraction (c) dark as there is no scattering (d) white as there is no scattering


Column A Column B

(A) Scattering (a) Twinkling of stars

(B) Total internal reflection (b) Formation of image by a plane mirror

(C) Refraction (c) Sparkling of diamond

(D) Reflection (d) Blue colour of the sky

(a) A → d; B → c; C → a; D → b (b) A → c; B → a; C → b; D → d (c) A → a; B → b; C → d; D → c (d) A → b; B → d; C → c; D → a

11. Arrange the following steps of an experiment to determine the focal length of a concave mirror in proper order.

(A) Focus the mirror to a distant object. (B) Place the concave mirror on a V shaped stand. (C) Measure the distance between the screen and the mirror. (d) Adjust the position of the screen, such that a clear image is formed on it. (a) BCAD (b) CDBA (c) BADC (d) BDAC

Chapter 5 Light 5.10

Space for rough work 12. A convex lens made of glass, with refractive index 32

, is placed in a medium

of refractive index 52

. A parallel beam of light entering the lens _______.

(a) diverges. (b) converges. (c) undergoes no refraction. (d) comes out as a parallel beam by itself.

13. The height of the image of an object placed in front of a convex lens is 4 cm. If the magnification produced by the lens is – 2, the height of the object is _______ cm and it is a _______ image.

(a) 2, real (b) 8, real (c) 8, virtual (d) 2, virtual

14. The critical angle of a prism is 42°. Choose the correct statement of a light ray incident on a prism as shown below.

60°

C B

A

(a) The angle of refraction on the surface AB is 30° (b) The angle of reflection on the surface AB is 60° (c) The angle of reflection on the surface AB is 30° (d) The angle of refraction on the surface AB is 42°

15. If a coin is placed at the bottom of a tank filled with water, upto a height 2 m, it appears to be at a depth of _______ from the surface of the water. (Refrac-

tive index of water is = 43

)

(a) 34

(b) 23

(c) 43

(d) 32




1. Choose the wrong statement (s) (a) The formation of an image is always due to the reflection. (b) Real images can not be formed due to the reflection of light. (c) The formation of a real image is always due to the refraction of the light

rays. (d) All of the above.

2. The point of intersection of incident rays is _________. (a) a real object (b) a real image (c) a virtual image (d) a virtual object

3. An optical instrument is placed inside a box as shown below. The incident rays and emergent rays are also shown. The optical instrument could be _________.

(a) a convex mirror (b) a concave mirror (c) a concave lens (d) either a concave lens or a convex mirror

4. Converging light rays incident on a convex mirror is as shown below. What is the image distance with proper sign convention?

20 cm 10 cm

(a) +10 cm (b) –10 cm (c) +20 cm (d) –20 cm

5. A convex mirror of focal length 20 cm forms an image whose size is one third of the size of the object. The object distance is _________ cm.

(a) 60 (b) 40 (3) 50 (d) 80

Chapter 5 Light 5.12

Space for rough work 6. A plane mirror is shifted towards an object by 5 cm. What is the shift in posi-tion of the image?

(a) 5 cm (b) 10 cm (c) 20 cm (d) 40 cm

7. The velocity of light in two media ‘X’ and ‘Y’ are 108 m s–1 and 1.5 × 108 m s–1, respectively. The refractive index of Y with respect to X is _________.

(a) 32

(b) 2 (c) 12

(d) 23

8. When a person suffering from short sightedness looks at an object at infinite distance, the focal length of the eye lens is _________ that of a normal eye.

(a) equal to (b) less than (c) greater than (d) double

9. In the evening hours, sky appears _________. (a) orange or red as light rays travel long distance (b) blue due to the scattering of light with lower wavelength (c) dark as there is no scattering taking place in the sky (d) white as there is no scattering taking place in the sky


Column A Column B

(A) Dispersion (a) Mirage

(B) Scattering (b) Pin hole camera

(C) Total internal reflection (c) Red light used as traffic signal

(D) Rectilinear propagation (d) Rainbow

(a) A → c, B → d, C → a, D → b (b) A → d, B → c, C → a, D → b (c) A → a, B → c, C → b, D → d (d) A → d, B → a, C → c, D → a

11. Arrange the following steps to determine the focal length of a convex lens in proper order.

(A) Focus the lens to a distant object. (B) Measure the distance between the lens and the screen. (C) Place the lens on a stand. (D) Adjust the position of the screen to obtain a clear image on it. (a) CABD (b) CBAD (c) CADB (d) CBAD


Space for rough work 12. A concave lens made of a material of refractive index 32

is placed in a

transparent liquid of refractive index 1.8. A parallel beam of light rays after passing through the lens _________.

(a) diverges (b) converges (c) undergoes not refraction. (d) emerges out as a parallel beam itself.

13. The height of the object placed in front of a convex lens is 20 cm. If the mag-nification is + 3, the height of the image is _________ cm and it is formed in the _________ side of the object.

(a) 60, same (b) 60, opposite

(c) 203

, same (d) 203

, opposite

14. The critical angle of the prism shown below is 42°. If the light ray enter a prism as shown below, choose the correct statement.

(A) Light ray emerges out from the side AC (B) Angle of deviation is 180° (C) Light ray does not undergo any refraction on the surface AB.

45°

45°

90°

A

C

B

(a) Only (B) (b) Only (C) (c) Both (B) and (C) (d) Only (A)

15. A stamp placed under a glass slab appears to be at a distance 4 cm from the top surface. Then the thickness of glass slab is _________ cm. (Refractive

index of glass =32

)

(a) 16 (b) 9 (c) 6 (d) 8

5.14 Answer Keys


1. (c) 2. (c) 3. (b) 4. (d) 5. (c) 6. (a) 7. (d) 8. (a) 9. (a) 10. (a) 11. (b) 12. (a) 13. (c) 14. (a) 15. (a)

Assessment Test II 1. (a) 2. (b) 3. (d) 4. (c) 5. (c) 6. (d) 7. (c) 8. (d) 9. (d) 10. (a) 11. (a) 12. (d) 13. (d) 14. (a) 15. (a)

Assessment Test III 1. (d) 2. (b) 3. (c) 4. (b) 5. (c) 6. (c) 7. (a) 8. (c) 9. (c) 10. (a) 11. (c) 12. (a) 13. (a) 14. (b) 15. (d)

Assessment Test IV 1. (d) 2. (a) 3. (c) 4. (d) 5. (b) 6. (b) 7. (d) 8. (b) 9. (a) 10. (b) 11. (c) 12. (b) 13. (a) 14. (c) 15. (c)



1. What happens when a glass rod is rubbed with silk cloth? (a) the electrons flow from glass rod to silk cloth. (b) the glass rod becomes a negatively charged body. (c) the glass rod becomes a positively charged body. (d) Both (a) and (c).

2. What happens when two identical bodies ‘A’ and ‘B’, which have +10 C and +5 C, respectively, are connected to each other by means of a metal wire?

(a) the conventional current flows from A to B. (b) the electronic current flows from A to B. (c) the electronic current flows from B to A. (d) Both (a) and (c).

3. An electrical conducting wire (ABCD) of negligible resistance is connected parallel to the resistor of R = 100 Ω as shown in the figure. If 2 × 1013 elec-trons are pushed into the circuit in every one second, then the current flow-ing through the conductor (ABCD) is _________. (charge of an electron = 1.6 × 10–19)

V

A D

R=100 Ω

B C

+ –

(a) 8 × 10–6 A (b) 1.6 × 10–13 A (c) 1.6 × 10–6 A (d) 3.2 × 10–6A

4. An electric device of 50 W is made to run for 20 h per day. If one unit costs ` 2.50, then the electric bill for the month of November is ` _________.

(a) 125 (b) 150 (c) 75 (d) 50


Electricity

Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Electricity; Page number - 8.1–8.27

Chapter 6 Electricity 6.2

Space for rough work 5. In which of the following electric circuits does the electric bulb shown glow?

(a) +

(b) + –

Silver

(c) + –

Silk hread

(d) + –

Silver wire

6. Assertion (A): When current is supplied by a cell, the cell gains electrons. Reason (R): The number of electrons coming out of the cell to the circuit is

equal to the number of electrons entering the cell from the circuit. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

7. Assertion (A): Mica sheets are placed on either side of the heating element.

Reason (R) : Mica does not conduct electricity but transfer the heat. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.


Column A Column B

(A) Chemical decomposition reaction (a) NH4Cl

(B) Dichromate cell (b) Metallurgical applications

(C) Chemical effect of electricity (c) Electrolyte

(D) Leclanché cell (d) K2Cr2O7 + H2SO4


Space for rough work (a) A → a; B → d; C → c; D → b (b) A → a; B → d; C → d; D → c (c) A → c; B → d; C → b; D → a (d) A → c; B → b; C → d; D → a

9. Two identical copper coins are melted and two wires ‘A’ and ‘B’ are made out of them. What is the resistance of B, if the length of A is twice that of B?

(a) equal to the resistance of A (b) equal to half the resistance of A (c) equal to quarter the resistance of A

(d) equal to 18

times the resistance of A

10. An electric fan consumes 1500 J of electrical energy in half–minute. The power of the fan is _________.

(a) 50 watt (b) 150 J s–1

(c) 45 watt (d) 200 J s–1

11. Based on the figure given below, four statements are given. Choose the correct statement among them.

+ −

A

S

B

CD

(a) Bulbs A,C and D are in series. (b) Bulbs A,B and D are in parallel (c) Bulbs A and B are in series (d) Bulbs C and D are in parallel to bulbs A and B

12. Leclanche cell consists of porous pot and a zinc rod placed in a solution of NH4Cl in a glass jar, the porous pot contains powdered carbon and MnO2 with carbon rod dipped in it.

(A) carbon rod acts as a positive electrode (B) zinc rod acts as a negative electrode

(a) Both A and B are correct (b) A is correct and B is incorrect (c) A is incorrect and B is correct (d) Both A and B are incorrect


Space for rough work 13. In which of the following, the principle of chemical effects of electricity is used?

(a) Telephones (b) Electroplating (c) Electric bell (d) Electric motor

14. In a domestic use, two fans of 100 W, three bulbs of 60 W each and 120 W of washing machine are used continuously for 10 h. Arrange the follow-ing steps to determine the amount of electrical energy consumed in proper sequence.

(A) Use the formula PEt

=

(B) Find the wattage of different electrical appliances and time for which they are used.

(C) Find the electrical energy consumed by each appliance. (D) Add them all and get the total electrical energy consumed. (a) DABC (b) BACD (c) DACB (d) BCAD

15. An electron revolves around a nucleus of an atom in an orbit of radius ‘r’ with a speed ‘u’. What is the electric current due to the motion the electron? (charge of the electron is represented as ‘e’)

(a) evr2 2π

(b) ev2

2

π (c)

evr2π

(d) ev

rπ




1. What happens when an ebonite rod is rubbed with fur? (a) the electrons flow from fur to ebonite rod. (b) the protons flow from fur to ebonite rod. (c) the ebonite rod becomes a positively charged body. (d) Both (b) and (c).

2. A charged body of charge –100°C is connected to the ground. Then _________. (a) the conventional current flows from the body to the ground. (b) the conventional current flows from the ground to the body. (c) the electronic current flows from the ground to the body because ground

is at zero potential. (d) Both (a) and (c).

3. An electrical conducting wire PQRS of negligible resistance is connected parallel to bulbs B1, B2 and B3 as shown in the figure. If 4 × 1018 electrons are emitted from the cell into the circuit, in each second, then the current flowing through the bulb B2 is _________ (The magnitude of charge of an electron is 1.6 × 10–19 C).

V

Q

B 3

R

P S B1B2

(a) 0 A (b) 0.64 A (c) 0.4 A (d) 6.4 A

4. Two electric bulbs of 100 W each are used for 10 h per day in the month of September. If the price of one unit is 3, then the electricity bill for two bulbs would be ` _________.

(a) 300 (b) 380 (c) 180 (d) 280


Space for rough work 5. In which of the electrical circuit diagrams given below, does electric bulb show a glow?

(a)

R

Switch

Silk thread

R

(b) + –

R R

Silk thread

(c) + –

R

R

(d)

Silver

+

6. Assertion (A): Insulators cannot conduct electricity. Reason (R): The electricity flowing through the solids is due to the flow of

free electrons in them and insulators have less number of free electrons. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.


Column A Column B

(A) Gold covering (a) Heating effect of electricity

(B) Button cell (b) Chemical effect of electricity

(C) EMF (c) Volt

(D) An electric stove (d) Zinc acts as anode


Space for rough work (a) A → d; B → a; C→ b; D → c (b) A → b; B → d; C→ c; D → a (c) A → b; B → a ; C→ c; D → d (d) A → a; B → c; C → b; D → d

8. Assertion (A): Magnesium oxide or quartz sand is used in a heater. Reason (R): Magnesium oxide or quartz sand has high electrical resistance

and is the most preferred material for the preparation of heating elements. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

9. The lengths of two silver rods ‘A’ and ‘B’, having the same mass, are in the ratio 2 : 3 and the resistance of A is _________ times the resistance of B.

(a) 1514

(b) 1415

(c) 49

(d) 53

10. An electric geyser consumes 10,000 J of electrical energy in 300 s to boil water. What is the power of the electrical greaser?

(a) 666.6 W (b) 333.33 W

(c) 33.33 W (d) 3 W

11. Five bulbs ‘A’, ‘B’, ‘C’, ‘D’ and ‘E’ are connected to each other as shown in the figure. Identify the correct statement from the statements given below.

+ –

S

C D

E

10V

(a) Bulbs A, B, C, D and E are connected in series. (b) The bulb E is connected in series to bulbs C and A. (c) The bulb C and D are in series and are parallel to the combination of A

and B and also parallel to E.

(d) Both (b) and (c).


Space for rough work 12. Choose the correct statement(s). (A) In a dry cell, the powdered carbon present in the electrolyte enhances

the flow of charge through it. (B) In lead–acid storage battery, the electrodes are made up of zinc or

carbon. (a) Both (A) and (B) are correct. (b) (A) is correct and (B) is incorrect. (c) (A) is in correct and (B) is correct. (d) Both (A) and (B) are incorrect.

13. Which of the following statements is not true with regards to Daniel cell? (a) It consists of a glass container which is divided into two unequal por-

tions by a porous membrane. (b) One portion contains ZnSO4 solution with a zinc rod dipped in it. (c) Another portion contains CuSO4 solution with a copper rod dipped

in it. (d) Electrons get accumulated over the zinc rod.

14. In a factory, 100 bulbs of 100 W, 100 fans of 60 W and 100 tube lights of 40 W are used for 10 h per day for 30 days. Arrange the following steps to calculate the total energy consumed, in a proper sequence.

(A) Find the energy consumed by bulbs, fans and tube lights. (B) Find the wattage of different electrical appliances from given data. (C) Find the total number of hours they are used in 30 days. (D) Add all the energies consumed by all appliances to get total energy.

(E) Use PEt

=

(a) EABCD (b) BECAD (c) BCEAD (d) ECABD

15. If a stream of He2+ ions passes through a cross section at the rate 2 × 1019 ions per second, then electric current due to the flow of ions is ________ A.

(a) 3.2 (b) 6.4 (c) 7.2 (d) 1.6




1. SI unit of electromotive force is _________. (a) newton (b) volt (c) ohm (d) coulomb

2. In an electric circuit electrons always move from _________ to _________ of the cell.

(a) lower potential to higher potential (b) negative terminal to positive terminal (c) higher potential to lower potential (d) Both (a) and (b)


Column A Column B

(A) Dry cell (p) 1.5 V

(B) Voltaic cell (q) 2 V

(C) Bichromate cell (r) 1.08 V

(D) Leclanche cell (s) 1.2 V

(a) A → s; B → q; C → r; D → p (b) A → p; B → r; C → q; D → p (c) A → s; B → r; C → p; D → q (d) A → s; B → p; C → q; D → r

4. Two bulbs each of 40 W and 50 W power are used for 15

th

of a day and 3

5

th of

a day, respectively. Write the following steps in a sequential order to find the total number of units consumed by them when they are used for 15 days.

(A) Convert the time into hours.

(B) Find the total energy (E) consumed by them in one day, i.e., E = E1 + E2.

(C) Write the energy in terms of units, i.e., commercial unit of electric energy.

(D) Find the electric energy consumed by each bulb in a day using E1 = P1t1 and E2 = P2 t2.

(E) Note down the powers of the bulbs and the time for which they are used per day as P1, P2 and t1 , t2, respectively.

(F) Now multiply E with 15 to get the energy consumed by them in 15 days. (a) AEDBFC (b) EADBCF (c) EADBFC (d) EABDCF


Space for rough work 5. The number of free electrons present in a certain volume of silver is _________ than the number of free electrons present in the same volume of aluminium.

(a) lesser (b) greater (c) neither greater nor lesser (d) None of these

6. Choose the correct one from the following. (a) Resistance is the amount of charge crossing unit cross-section of a con-

ductor in 1s. (b) Resistance is inversely proportional to the square of the radius of the

wire. (c) Electrostatic force depends on the medium between the two charges. (d) Both (b) and (c)

7. Which of the following has the defects like local action and polarization? (a) Daniel cell (b) Voltaic cell (c) Leclanche cell (d) Dry cell

8. What happens when a neutral body is brought in contact with a negatively charged body?

(a) it becomes positively charged. (b) it becomes negatively charged. (c) the net charge is zero. (d) it consists of equal positive and negative charges.

9. If an electric current of 5 A flows through a circuit which consists of a bulb, then the number of electrons passing through the bulb in 2 minutes is ________.

(a) 3750 × 1019 electrons (b) 3.75 × 1021 electrons (c) 3.75 × 1019 electrons (d) 3.75 × 10–19 electrons

10. A 60 W bulb is switched ON for 20 h. What is the energy consumed in com-mercial unit?

(a) 120 kWh (b) 120 unit (c) 1.2 unit (d) 3 unit


Space for rough work 11. What is the charge developed, if a body gains 50 × 1018 electrons by rubbing it with another body?

(a) 2 C (b) 16 C (c) +8 C (d) –8 C

12. A 60 W bulb is used 10 h per day. If the cost of electricity is ` 4 per unit, then the bill for the month of February in a leap year is _________.

(a) ` 240 (b) ` 70 (c) ` 120 (d) ` 75

13. The length and radius of ‘a’ wire are ‘’ and ‘r’, respectively, and its resist-ance is ‘R’. If the length and radius are doubled, then its new resistance _________.

(a) remains same (b) is doubled

(c) is R2

(d) is R4

14. If 1, 2 and r1, r2 are the length and radius of cross-section of two wires made

of the same material and

rr

1 22

2 12

= 14

, then the ratio of resistance of two wires

is _________.

(a) 4 : 1 (b) 1 : 16 (c) 1 : 4 (d) 16 : 1

15. Six identical bulbs B1, B2, B3, B4, B5 and B6 are connected to a cell in the fol-lowing manner.

V

If V = 20 V and the resistance of the each bulb is = 2 Ω, then total current in the given circuit is ________

(a) 40 A (b) 11.11 A (c) 16.6 A (d) 1.6 A




1. SI unit of an electric charge is _________. (a) volt (b) ampere (c) coulomb (d) farady

2. Inside a cell, the conventional current flows from _________. (a) negative terminal to positive terminal (b) lower potential to higher potential (c) higher potential to lower potential (d) both (a) and (b)

3. Match the entries of Column A with those of Column B by using a relation,

F = q qr

14 0

1 22πε

.

Column A Column B

(A) Electrostatic force between the charges q1, q2 at a distance 2r is

(p) 16F

(B) Coulomb force between the charges 2q1, 2q2, at r2

distance is(q) 0 F

89

(C) Force between the charges 2q1, q2 at 2r distance is (r) F4

(D) Force between the charges q1, 2q2 at r32

distance is (s) F2

(a) A → r; B → s; C → p; D → q (b) A → r; B → p; C → q; D → s (c) A → p; B → r; C → s; D → q (d) A → r; B → p; C → s; D → q

4. If 4 A of current flows through a conductor in one minute, how many num-ber of charge carriers passed through it? Write the following steps in a sequential order to find the number of electrons that passed through a con-ductor in one minute.

(A) Equate (1) and (2), to find the number of electrons. (B) Find the charge (Q) that follows through the circuit using Q = _________

(current x time) _________ (1).


Space for rough work (C) Note the given data about current (i) and time (t). (D) The number of electrons (n) flowing through the circuit can be found

using Q = ne._________ (2). (a) BCDA (b) CBDA (c) CDBA (d) CDAB

5. The number of free electrons per unit volume is more in _________. (a) glass (b) graphite (c) iron (d) water

6. Choose the incorrect one from the following: (a) Charge density is the product of charge and surface area. (b) Carbon is not used as positive electrode in lead-acid storage battery. (c) Polarisation and local action are the defects of Leclanché cell. (d) Both (a) and (c)

7. Which of the following has ammonium chloride as an electrolyte? (a) Voltaic cell (b) Dry cell (c) Leclanche cell (d) Both (b) and (c)

8. When a neutral body conceded to earth is brought closer to a negatively charged body, then

(a) it becomes negatively charged. (b) it consists of equal positive and negative charge. (c) it becomes positively charged. (d) no change in charge on it.

9. If the power of the bulb is 40 W and its resistance is 10 Ω, then the amount of current passing through it in 1 s is _________.

(a) 4 A (b) 5 A (c) 40 A (d) 2 A

10. A bulb consumes 4,000 J of energy in 50 s, then the power of the bulb is _________.

(a) 60 W (b) 40 W (c) 80 W (d) 100 W

11. What is the charge on ‘X’, if a body X loses 125 × 1018 electrons by rubbing it with another body ‘Y’?

(a) +20 C (b) +2 C (c) –8 C (d) –20 C


Space for rough work 12. The cost of one unit of electricity is ` 5. If the bill is ` 200, then the number of units consumed is _________.

(a) 20 units (b) 60 units (c) 50 units (d) 40 units

13. Two wires of the same length but different radii are having their resistance ratio 1 : 9. If the radius of the first wire is 'r', then the radius of the second wire is _________.

(a) r3

(b) r2

(c) r (d) r9

14. Two wires made of same material are having the lengths 1, 2 and ratio r1, r2. If 1 : 2 = 1 : 1 and r1 : r2 = 1 : 2, the ratio of their resistance R1 : R2 is _________.

(a) 2 : 1 (b) 1 : 4 (c) 4 : 1 (d) 1 : 2

15. In the figure given below, what is the ratio of potential across AB and CD, if all the bulbs are identical?

A B

C D• • • •

(a) 1 : 1 (b) 5 : 4 (c) 4 : 1 (d) 4 : 5

6.15Answer Keys


1. (d) 2. (d) 3. (d) 4. (c) 5. (c) 6. (d) 7. (a) 8. (c) 9. (c) 10. (a) 11. (c) 12. (a) 13. (b) 14. (b) 15. (c)

Assessment Test II 1. (a) 2. (b) 3. (a) 4. (c) 5. (d) 6. (b) 7. (b) 8. (c) 9. (b) 10. (c) 11. (c) 12. (b) 13. (a) 14. (c) 15. (b)

Assessment Test III 1. (b) 2. (d) 3. (b) 4. (c) 5. (b) 6. (d) 7. (b) 8. (b) 9. (b) 10. (c) 11. (d) 12. (b) 13. (c) 14. (c) 15. (b)

Assessment Test IV 1. (c) 2. (d) 3. (d) 4. (b) 5. (c) 6. (d) 7. (d) 8. (c) 9. (d) 10. (c) 11. (a) 12. (d) 13. (a) 14. (c) 15. (c)



1. Assertion (A): Direct current (DC) and alternating current (AC) both are used for the electrical method of magnetisation.

Reason (B): Direct current and alternating current produce constant magnetic field.


2. Arrange the following steps in sequential order to magnetize a steel bar with a strong permanent magnet.

(A) Keep the steel bar to be magnetized on a wooden table. (B) Take a strong permanent magnet and bring one pole (say north pole) of

the magnet near one end of the steel bar and gently rub from one end. (C) Once it has reached the other end, lift the magnet gently away from the

steel bar and again bring it to the starting end. (D) Repeat this process several times so that the steel bar is magnetized with

the starting end as the north pole and the other end as the south pole. (a) ACBD (b) BACD (c) ABCD (d) ADBC

3. A substance which is feebly repelled by a magnet is a __________. (a) diamagnetic substance. (b) paramagnetic substance. (c) ferromagnetic substance. (d) none of the above.

4. The equatorial meridian of a magnet __________. (a) bisects the magnetic axis perpendicularly. (b) is parallel to the magnetic axis. (c) makes a certain angle with the magnetic equator. (d) contains both the poles of the magnet.


Magnetism and Our Universe

Reference: Coursebook - IIT Foundation Physics Class 8; Chapter - Magnetism; Page number - 9.1–9.15; Coursebook - IIT Foundation Physics Class 7; Chapter - Our Universe; Page number - 8.1–8.15;

Chapter 7 Magnetism and Our Universe 7.2


Column A Column B

(A) Like poles (a) Attraction

(B) Unlike poles (b) Resultant magnetic field is zero

(C) Null points (c) Magnetic flux

(D) Magnetic field lines passing perpendicular to a given area

(d) Repulsion

(a) A → d; B → b; C → a; D → c (b) A → d; B → a; C → b; D → c (c) A → b; B → d; C → a; D → c (d) A → c; B → a; C → d; D → b

6. Assertion (A): Magnetic lines of force never intersect each other. Reason (R): It they intersect, there will be two directions for the magnetic field which is impossible. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

7. In the diagram given below, if ‘x’ is a neutral point, magnetic poles ‘A’ and ‘B’ are __________and __________, respectively.

x

A B

(a) North, South

(b) North, North

(c) South, North

(d) South, South

8. Magnetic field lines are __________.

(a) closed continuous curves.

(b) directed from north pole to south pole in the magnetic field.

(c) directed from south pole to north pole inside the magnet.

(d) All of the above.


Space for rough work 9. Magnetic induction depends on _________.

(a) nature of the medium

(b) strength of inducing the magnet

(c) nature of the magnetic substance

(d) Both (b) and (c).

10. In the Sun, hydrogen is converted to _________.

(a) helium. (b) oxygen.

(c) carbon. (d) nitrogen.

11. 1 light year = _________ m

(a) 9.46 × 1015 (b) 2.46 × 1015

(c) 15 × 1015 (d) 20 × 1015

12. The angle of declination is _________.

(a) 90° at the poles (b) 0° at the equator

(c) variable (d) constant

13. The magnetic moment of a bar magnet ‘A’ and its length are half that of another bar magnet ’B‘. Arrange the following steps in sequential order to find the ratio of their pole strengths.

(A) Write the given values of magnetic moment (M) and magnetic length 2( ) of the bar magnets A and B.

(B) Write the expression for pole strength (m) for each magnet using M2

.

(C) Divide the two expressions to get the ratio of mA to mB

(1) BAC (2) ACB

(3) BCA (4) ABC

14. What happens when a magnet is broken into two parts? (a) the smaller part acts like the north pole. (b) the bigger part acts like the north pole. (c) both the parts will have both the poles. (d) polarity of each part depends upon the material.

15. Choose a suitable option for a current carrying straight conductor. (a) south and north poles do not exist. (b) south pole and north pole are present but cannot be found. (c) one face is the north pole and the other is the south pole (4) no lines of force can be drawn.




1. Assertion (A): When an iron piece is magnetized, its length slightly increases.

Reason (R): The closed molecular chains break down and all molecules align themselves in the direction of external magnetic field.


2. Arrange the following steps in sequence for plotting the magnetic lines of force around a bar magnet.

(A) Place a bar magnet NS on the line such that its axial line coincides with the line on the paper and mark its boundary.

(B) Draw a line in the middle of a white paper fixed on a drawing board. (C) Repeat the procedure by shifting the compass and mark the points

2, 3, 4, etc. (D) Take a plotting compass and place it near the north pole of the bar mag-

net and mark the point 1 in the direction in which the north pole of the plotting compass points.

(E) Join the points 1, 2, 3 ……. by a smooth curve (a) ABCDE (b) BADCE (c) ACBDE (d) BACDE

3. Which is an example of diamagnetic substance? (a) Platinum (b) Iron (c) Gold (d) Nickel

4. Physical length of a bar magnet is _________ magnetic length. (a) less than (b) greater than (c) equal to (d) may be less or greater than


Column A Column B

(A) Magnetic field (a) Same angle of declination

(B) Magnetic field lines (b) Angle of dip is zero

(C) Isogonic line (c) Never intersect

(D) Aclinic line (d) Region in space where the effect of a magnet is felt.


Space for rough work (a) A → d; B → c; C → a; D → b (b) A → d; B → c; C → b; D → a (c) A → c; B → d; C → a; D → b (d) A → b; B → c; C → d; D → a

6. Assertion (A): Steel is used for making a permanent magnet. Reason (R): Retentivity of steel is high. (a) A and R are true and R is the correct explanation of A. (b) A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) Both A and R are false.

7. In the diagram, the magnetic poles ‘X’ and ‘Y’ are _________ and _________, respectively.

X Y

(a) South, North (b) North , South (c) South, North (d) North, North

8. Which of the following is the test for magnetism? (a) conduction (b) induction (c) repulsion (d) attraction

9. Light year is the unit of _________. (a) time (b) average intensity of sunlight in one year (d) distance (d) period of revolution of earth around sun

10. If it takes 8 min and 20 s for sunlight to reach the Earth, the distance between the Earth and the Sun is _________. (The velocity of light is 3 × 108 m s–1)

(a) 5 × 1010 m (b) 10 × 1010 m (c) 15 × 1010 m (d) 20 × 1010 m

11. The angle made by the Earth’s magnetic field with its vertical component is 60°, the angle of dip at the place is _________.

(a) 60° (b) 30° (c) 90° (d) 0°


Space for rough work 12. A bar magnet has a pole strength of 10 A-m. If the distance from its centre to either of the poles is 5 cm, arrange the following steps in sequential order to find its magnetic moment in SI unit.

(A) Substitute the values in the above formula to get the value of M. (B) Write the given value of pole strength (m) of the magnet. (C) Find the value of magnetic length 2( ) of the magnet from the problem

and convert it into SI unit. (D) Write the required formula, i.e., magnetic moment (M) = mx 2l

(a) BCDA (b) ABDC (c) BDCA (d) ABCD

13. Magnetic keepers, used to prevent loss of magnetism, must be made of _________.

(a) wood (b) copper (c) soft iron (d) Both (b) and (c)

14. What happens when a small steel rod is brought near a bar magnet? (a) magnetism is induced in the steel rod and it gets attracted to the magnet. (b) the steel rod becomes a magnet and the bar magnet loses its magnetism. (c) the steel rod first gets attracted and then magnetism is induced in it. (d) the steel rod destroys the magnetic properties of the bar magnet.

15. Why do meteors seldom reach the Earth? (a) freezing caused when they pass through the atmosphere. (b) greater force of attraction towards the Sun. (c) greater force of attraction towards the Moon. (d) vapourization is caused when they pass through the atmosphere.




1. In our solar system which of the following planets has high orbital speed?

(a) Earth (b) Mars

(c) Mercury (d) Jupiter

2. Among the following, pick out the odd one.

(a) Phobos (b) Shoemaker levy

(c) Deimos (d) Moon

3. The retentivity is high for _________.

(a) soft iron bar (b) steel bar

(c) aluminium bar (d) copper bar


Column A Column B

(A) SI unit of pole strength (a) A – m2

(B) Magnetic keeper (b) Tesla

(C) SI unit of magnetic moment (c) A – m

(D) SI unit of magnetic field induction

(d) Prevents loss of magnetism.

(a) A → c; B → b; C → d; D → a (b) A → c; B → d; C → b; D → a (c) A → c; B → d; C → a; D → b (d) A → d; B → c; C → a; D → b

5. Following are the steps to magnetize a steel bar. Arrange them in a sequen-tial order.

(A) The end at which current enters in an anti-clockwise direction will become the north pole and the other end becomes the south pole.

(B) Keep the steel bar to be magnetized inside a long coil of insulated cop-per wire.

(C) Pass a strong direct current through the coil for sometime. (D) The specimen of steel bar will get magnetized.

(a) CBDA (b) BDCA

(c) BADC (d) BCDA


Space for rough work 6. Arrange the following diagrams in a sequential order from a new moon day to full moon day.

(A)

(B)

(C) (D)

(E)

(a) EABDC (b) DABCE (c) EACBD (d) ECABD

7. Synodic month is of _________.

(a) 2912

days from one new moon to the next new moon.

(b) 30 days from one new moon to the next new moon. (c) 15 days from one new moon to the next full moon.

(d) 2712

days from one full moon to the next full moon.

8. Which of the following materials is/are feebly repelled by a magnet? (a) Water (b) Aluminium (c) Platinum (d) Both (a) and (b)

9. Ewing’s molecular theory could not explain _________. (a) ferromagnetism (b) saturation of magnetism (c) the existence of dipoles (d) Both (a) and (c)

10. Angle of inclination always _________. (a) remains constant (b) varies from 0° to 90° (c) varies from 0° to 30° (d) varies from 0° to 60°

11. The strength of a magnetic flux density increases as _________. (a) the distance between the magnetic poles increases. (b) the magnetic strength increases. (c) the number of magnetic lines of force passing through a given area

increases. (d) both (b) and (c).


Space for rough work 12. From the figure given below, choose the points where the net magnetic field induction is zero.

D

B

C

x

A

x

•

•

• •

(a) B (b) C (c) A (d) D

13. Choose a planet from the following that rotates from east to west. (a) Venus (b) Mars (c) Saturn (d) Jupiter

14. A bar magnet of pole strength 2 × 10–2 A–m has its effective length 8 cm. What is its magnetic moment?

(a) 16 × 10–4 A–m (b) 1.6 × 10–3 A–m2

(c) 16 m A–m2

(d) 16 × 10–3 A–m

15. Geostationary satellite is launched in the orbit at a height _________ from the Earth’s surface.

(a) 30,000 km (b) 36,000 km (c) 36,000 m (d) 30,000 m




1. Which of the following planet has the minimum orbital speed?

(a) Saturn (b) Venus

(c) Jupiter (d) Neptune

2. Pick out the correct one that is similar to the planet Saturn.

(a) Uranus (b) Jupiter

(c) Neptune (d) All of the above

3. What does retentivity mean? (a) magnetism in the presence of applied magnetic field. (b) retaining magnetism in the absence of applied magnetic field. (c) an ability of the medium to allow magnetic lines of force. (d) the force of attraction or repulsion between two magnetic poles.


Column A Column B

(A) Jovian planets (a) Soft iron

(B) Espionage (b) Steel

(C) Permanent magnet (c) Saturn

(D) Electromagnet (d) Spying the movement of enemy troops

(a) A → c; B → b; C → d; D → a (b) A → c; B → d; C → b; D → a (c) A → c; B → b; C → a; D → d (d) A → d; B → c; C → a; D → b

5. The strength of a bar magnet is 10 A-m. If the distance from its centre to either of the poles is 10 cm. Arrange the following sentences in sequential order to find its magnetic moment in SI unit.

(P) Note down the value of length ‘l’ of the magnet from the problem and convert it into SI unit.

(Q) Substitute the values in the above formula to get the value of M.

(R) Write the given values of pole strength ‘m’ of the magnet.


Space for rough work (S) Write the formula, magnetic moment, (M) = m × 2 (a) PQRS (b) SPQR (c) RPSQ (d) PRSQ

6. Arrange the following planets in the increasing order of their orbital speed around the Sun.

(A) Earth (B) Venus (C) Mars (D) Jupiter (a) EDBA (b) ADCB (c) CBDA (d) DCAB

7. The average time gap between one full moon and the next full moon is _________ days.

(a) 15 (b) 30 (c) 29.5 (d) None of these

8. Which of the following material is/are strongly attracted by a magnet? (a) Chromium (b) Cobalt (c) Gold (d) Aluminium

9. Ewing’s molecular theory explained _________. (a) saturation of magnetism (b) directionality (c) attractive (or) repulsive nature of poles (d) All of the above

10. What is angle of inclination? (a) The angle made by the Earth’s magnetic field with its horizontal

component. (b) The angle made by magnetic meridian with geographic meridian. (c) The angle made by the Earth’s magnetic field with its vertical component. (d) The angle made by the Earth's geographic meridian with its horizontal

component.

11. The magnetic force between any poles is _________. (a) directly proportional to the product of their pole strengths. (b) directly proportional to the square of the distance between them. (c) inversely proportional to the square of the distance (d) Both (a) and (c)

7.12 Answer Keys

Space for rough work 12. From the figure given below, choose the points where we will observe approximately similar magnetic field strength.

• •

•

B

D

C

A

X

X

(a) A and D (b) B and C (c) C and D (d) A and D

13. Which of the following is called Canis Major? (a) Alpha century (b) Sun (c) Orion (d) Sirius

14. Consider a bar magnet of pole strength ‘m’ and with effective length ‘2ℓ'. If the bar magnet is made into two pieces along its equatorial line, then its magnetic moment is _________.

(a) lm (b) m2

(c) 2lm (d) m4

15. What is the time period of a geostationary satellite? (a) 24 min (b) 30 h (c) 48 h (d) one mean solar day


1. (d) 2. (c) 3. (a) 4. (a) 5. (b) 6. (a) 7. (b 8. (d) 9. (d) 10. (a) 11. (a) 12. (c) 13. (d) 14. (c) 15. (a)

Assessment Test II 1. (a) 2. (b) 3. (c) 4. (b) 5. (a) 6. (a) 7. (c) 8. (c) 9. (c) 10. (c) 11. (c) 12. (a) 13. (c) 14. (a) 15. (d)

Assessment Test III 1. (c) 2. (b) 3. (b) 4. (c) 5. (d) 6. (b) 7. (a) 8. (a) 9. (a) 10. (b) 11. (d) 12. (c) 13. (a) 14. (b) 15. (b)

Assessment Test IV 1. (d) 2. (d) 3. (b) 4. (b) 5. (c) 6. (d) 7. (c) 8. (b) 9. (d) 10. (a) 11. (d) 12. (b) 13. (c) 14. (a) 15. (d)

Assessment Test I

1. The mass of a body remains constant and is the inherent property of the body. Weight: w = mg. The weight of the body changes with a change in the value of acceleration due to gravity (g).Hence, the correct option is (d).

2. aVt

V ut

= =−∆

∆The SI unit of velocity is m s–1 and for time, it is second (s).⇒ The SI unit of acceleration is

a = =-

-m ss

m s1

2 .

Hence, the correct option is (a).

3. Take a stone (irregular shape) and a measuring jar. Fill the vessel with liquid and water and immerse the stone in it. The difference in the volume of the liquid is equal to the volume of the stone.Hence, the correct option is (b).

4. Here, u = 50 m s–1; v = 60 m s–1; t = 0.1 s; (i)

Using the equation of motion, V = u + at (ii)

From above equation, aV u

t=

− (iii)

a60 50

0.1100 m s 2⇒ =

−= − (iv)


5. (A) → b Physical quantity is a measurable quantity

(B) → a Volume of a drop of a liquid can be measured using a burette

(C) → d The SI unit of instantaneous speed is m s–1

(D) → c Acceleration is defined as the rate of change of velocity.Hence, the correct option is (a).

6. 1 M. S. D = 0.1 cm = 1 mmN = 20

= = =N

L.C.1 M.S.D. 1 mm

200.05 mm.

Hence, the correct option is (c).

7. = = =1 M.S.D.1 cm

100.1 cm 1 mm

= = =N

L.C.1 M.S.D. 1 mm

100.1 mm.

M. S. R = 3V. C. D = 4l = M . S . R + (V. C. D × L. C.) = 3 mm + 4 × 0.1 mm = 3.4 mm.Hence, the correct option is (b).

Hints and Explanations

CHAPTER 1Measurements and Kinematics

Chapter 1 Measurements and KinematicsA.2

8. Average speed =Total distance

Total time taken

Its CGS unit is cm s–1.Hence, the correct option is (b).

9. Relative density of gold is 19.Hence, the correct option is (c).

10. u = 120 km h–1 1205

18100

3m s 1= × = −

V = 0 km h–1 = m s–1

t = 4 s

aV u

t

0100

34

10012

253

m s 2=−

=−

= − = − −

∴ Deceleration253

m s .2=

Hence, the correct option is (b).

11. l = 330 mt = 40 s

=VSt

Average velocity,Total displacment( )Total time taken ( )

Here, the athlete comes back to his original position. So,

S

= 0

V

040s

0 m s 1⇒ = = −


12. When a body moves with a uniform (constant) velocity, then its instantaneous velocity will be equal to the average velocity. Hence, its accel-eration is equal to zero.Hence, the correct option is (d).

13. t1= 1h t2= 1h

v2= 100 km h–1S2

v1= 100 km h–1S1

B C× ××

A

vS

tS v t1

1

11 1 1 500= ⇒ = = km

vS

tS U t2

2

22 2 2 100= ⇒ = = km

Average speed,Total distance

Total time taken= =

++

S S

t t1 2

1 2

= = −1502

75 1 km .

Hence, the correct option is (d).

14. Here the body covers 100 m in 10 sThe body travels in a straight path, then displacement,

S

= 100 m and t = 10 s. The average velocity,

= = −V

100m10s

10 m s 1

= = = −St

And average speed,100m10s

10 m s 1

Both (A) and (B) are true.


15. Given: u = 0: a = 2 m s–2: t = 10 sV = u + at = 0 + 2 × 10 = 20 m s–1

∴ =+

=+

= −u vAverage velocity

20 20

210 m s .1


Assessment Test II

1. Mass of a body remains constant and mass is an inherent property of the body.Hence, the correct option is (a).

2. When a vehicle moves in a straight path, then its average speed is equal to its average velocity.Hence, the correct option is (a).

3. Place the metallic sphere between the jaws of a vernier caliper and note M. S. R and V. S. R from the given data.Here diameter, (D) = M. S. R + (V. C .D × L. C)

Hints and Explanations A.3

Substitute the values and obtain the diameter of the sphere. The radius of the metallic sphere is equal to half of the diameter.


4. Given data: u = 90 km h–1; v = 0; s = 200 m

= × = −u 905

185ms 1 (ii)

Use the equation of motion, u v st2

+= (iii)

Substitute the values of u, v, s in above equation (i)

Then, the value of t = +s

u v2

(iv)


5. (A) → d Velocity is a derived quantity. It is derived from displacement and time.

(B) → c Displacement has both magnitude and direc-tion. It is a vector quantity.

(C) → b Roman steelyard is used in hardware shop.

(D) → a Ampere (A) is unit of current, which is a fun-damental physical quantity.Hence, the correct option is (a).

6. Given: 1 M. S. D = 12

mm;

V. C. D = 8; L. C = 0.05 mm;

M. S. R = 22 M. S. D = 22 × 12

mm = 11 mm

l = M. S. R + (V. C × L. C) = 11 mm + (8 × 0.05 mm) = (11 + 0.40) mm = 11.40 mm.Hence, the correct option is (d).

7. Given: 1 M. S. D = = =2

2020

201

cm mm mm;

1 V. S. D = 0.9 mm

L. C = 1 M. S. D − 1 V. S. D

= 1 mm − 0.9 mm

= 0.1 mm.Hence, the correct option is (b).

8. SI unit of amount of substance is mol and there is no CGS unit.Hence, the correct option is (d).

9. Given: dsinker = 6 g cm–3 = 6000 kg m–3

dliquid = 2000 kg m–3 = 2 g cm–3.

Here dsinker > dliquid


10. Given: u = 20 m s–1; V = 0; s = 100 m; t = 10 s

=−

=−

= − −av u

t0 200

1020 m s 2


11. Given: l = 13

m; n = 1000 rotations; t = 20 s

Average velocity Totaldisplacement

Total timeV

=

= =0

0t

.


12.

3 m5 m

C

B4 m

A

Using Pythagoras theorem, AC2 = AB2 + BC2 ⇒ BC2 = AC2 − AB2

= 52 − 42

= 25 − 16 = 9 ⇒ BC = 9 = 3 mDistance covered by toy car, s = 4 + 3 = 7 mDisplacement of the car,

s = 5 m.

∴

=ss

57



13. s/2 s/2

t1

v1=10 km h-1

t2

v2

×× ×

Here v1 =

s

tt

ss2 2

10 2011⇒ = =

v2 =

s

tt

s

v2 2

222

2

⇒ =

Average speed, V = Totaldistance

Total time taken

⇒ 15 =

s s

t ts

s s v2 2

20 21 2 2

+

+=

+

15 = ( )+

=+

s

sv

v

v

s v2 2040

40

102

2

2

2

40 v2 = 30 v2 + 300

⇒ v2 = 30 km h–1 = v.


14. When a body is moving in a straight path, then its instantaneous speed is equal to instantane-ous velocity and its average speed is equal to its average velocity.Hence, the correct option is (d).

15. Given: t1 = 9 a.m.; t2 = 8 p.m.⇒ Δ T = t2 − t1 = 11 hDistance travelled; s = ?Average speed, v = 20 km h–1

vst

=

s = v × t = 20 × 11 = 220 km

Odometer reading at 8 p.m. is

∴ 4700 + 220 = 4920.


Assessment Test III

1. Candela is the unit of luminous intensity.Hence, the correct option is (c).

2. Least count = 1 M.S.D. – 1 V.S.D.

= −

=−

= =

1 mm1920

mm

20 mm 19 mm20

120

0.05 mm


3. N V.S.D. = (N – 1) M.S.D.Hence, the correct option is (c).

4. Relative density =density of substance

density of water

0.9 = d1

∴ d = 0.9 g cm-3 = 900 kg m–3


5. Given, Volume drained = 40 mLNumber of drops = 20

∴ Volume of 1 drop =4020

= 2 mL


6. 1 kg m 1 s–2 = ( )−1000 g

100cms 2

= 10 g cm–1 s–2


7. A → r, B → p, C → q Length – mile Electronic current – ampereTime – yearHence, the correct option is (c).

8. Volume1 = 100 cm3

v2 = 150 cm3

m1 = m2


dd

mv

vm

150100

32

1

2

1

1

2

2

= × =

=


9. Area = 2 × 5 + 12

5 2227

1 2× × −

( )

=10 + 5 − 227

∴ 15 – 3.14 = 11.86 cm2


10. h =FxAv

×=

Nm

m ms

Nsm2 2


11. 1 M.S.D. = 1 mmN = 20V.C.D. = 16M.S.R. = 12.3 cm = 123 mm = M.S.R. + V.C.D. × L.C

= 123 + 16 × 120

= 123.8 mm

∴ Radius = 123.8 = 61.9 mmHence, the correct option is (b).

12. kg m s–2 = 1000 g × 100 cm × s–2

= 105 g cm s–2

\ =SI unit

CGSunit105


13. L.C = 1 M.S.D. – 1 V.S.D. = 1 mm – 0.8 mm = 0.2 mmHence, the correct option is (c).

14. V = 200 cm3

Mass = 400 g

Density =Mass

Volumeg cm= = −400

2002 3

∴ Relative density = 2Hence, the correct option is (a).

15. M.S.R. = 7 mmV.S.R. = 8Reading = M.S.R. + (V.S.R. × LC)

= 7+ 81

10×

=7.8 mm


Assessment Test IV

1. Speedometer is a device which is used to find instantaneous speed.Hence, the correct option is (a).

2. =−1 ms185

km / h1

∴ 5 m s–1 = ×5185

km / h

= 18 km h–1


3. Because acceleration is change in velocity per unit time.Hence, the correct option is (d).

4. In displacement–time graph, the slope indi-cates velocity.Hence, the correct option is (a).

5. The physical quantity which has both magni-tude and direction is called vector. Here, velocity has both magnitude and direction. Hence, the correct option is (a).

6. A → c, B → a, C → d, D → b.Hence, the correct option is (a).


7. S = ut at12

2+

S4 = 0 412

6 42× + × × = 48 m

S3 = 0 312

6 32× + × × = 27 m

∴ Displacement in 4th second is = 48 – 27 = 21 mHence, the correct option is (b).

8.

W

S

E

N

13 m

5 m8 m CAB

AB = 8 m, BC = 13 m, AC = 5 mDistance = 21 m, displacement = 5 m Hence, the correct option is (b).

9. As the person comes to the same position after 4 rotations, the displacement is zero.Hence, the correct option is (b).

10. A

6 m

B C

45°

45°

AB = height of building = 6 m

A = initial position

C = final position

As ΔABC isosceles triangle AB = BC

(AB = 6 m given)

BC = 6 mAC = displacement

AC = AB BC2 2+

= 6 62 2+ = 72

= 36 2× = 6 2 m

∴ Displacement is 6 2 mHence, the correct option is (b).

11. 2 s4 s

24 m 21 m

B CA• • •

Case I: A → B

Initial velocity = u

t = 4 s s = 24 m

S = ut at12

2+

24 = u a412

16× + × ×

24 = 4u + 8a

⇒ 6 = u + 2a (i)

Case II: A → CInitial velocity = ut = 6 ss = 45 ms = ut+ 1/2at2

45 = u a612

36+ × ×

45 = 6u + 18a

15 = 2u + 6a (ii)(ii) – 2 × (i)15 = 2u + 6a

–12 = 2u + 4a

– – – 3 = 2a a = 1.5Substitute in (i), we get6 = u + 2a

6 = u + 2(1.5)u = 3∴ Initial velocity = 3 m s–1


12. 10 s

100 m 50 m

A• • •

B C

Case I : A → B

Initial velocity = u = 0

t = 10 s S = 100 m

By s = ut + 1/2at2


100 = a12

100× ×

a = 2 m s–2

VB = u + at

= 0 + 2 × 10 = 20 m s–1

Case II : B → C

u = 20 m s–1 v = 0 m s–1 s = 50 m

By av u

s

=

−=

−×

2 2 2 2

20 202 50

=−

= −400

1004

a = –4 m s–2; a 4ms 2=→

−


13. No body can have different velocities at the same time.Hence, the correct option is (a).

14. P• • •

B PB

10 m

Let V be the velocity. Then distance covered by person in time t = Vt and distance covered by the bus in the same time.

Sb = ut at12

2+

x = × ×12

0 1 30 2. ( )

= 45 m55 = V × 30

V =5530

=116

= 1.83 m s–1.Hence, the correct option is (d).

15. Y

V

10 m s−1

10 s 15 s 12 sBAO

D E

C X

As we know that area under v – t graph is distance covered distance covered = Total area

= × + × + ×12

12

OA AD AB AD BC BE

= × × + × + × ×12

12

10 10 15 10 12 10

= 50 + 150 + 60 = 260 mHence, the correct option is (d).

Assessment Test V

1. Candela is the SI unit of luminous intensityHence, the correct option is (c).

2. L.C = 0.05 mm

=M

L.C1 M.S.D.

= = =N1

0.05100

520


3. =L.C1 M.S.D.1 V.S.D.

is incorrect.


4. Relative densitydensity of substance

density of water=

51

5= = -dd, g cm 3



5. Volume of 1 drop = 0.3 mLVolume of drops = 30

0 350

30. =

−x

x = 59∴ Initial level of the liquid = 59


6. 1 kg m s–1 = 100 g × 100 cm × s–1

= 105 g cm s–1.Hence, the correct option is (d).

7. A → q, B → r, C → p; amu is the unit of mass. The unit of time is day and the unit of length is foot. Hence, the correct option is (c).

8. d

d

mvmv

m

m1

2

1

1

2

2

1

2

2 3= = = :


9. Area = [10 × 6] +

227

7 72

227

3 512

2 32××

− ×

− × ×

( . )

= 140 + 77 – 38 – 5 = 172.5 cm2


10. =−

−kg mskg

m

m s1

1

∴ The quantity is speed.Hence, the correct option is (b).

11. 1 M.S.D. = 1 mm

N = 40, V.C.D. = 28, M.S.D. = 12 mm

l = M.S.R. + V.C.D. × C

= + ×112 28140

= 112.7 mmHence, the correct option is (b).

12. CGS unit = g cm2


13. N = 20, 1 M.S.D. = 1 mmL.C = 0.3 mmAs least count is 0.3 mm

=n

N0.3

M.S.D.

0 3. =n10

n = 3∴ The formula is,

=N

L.C.3 M.S.D.

∴ The principle is V.S.D. = (N – 3) M.S.D.Hence, the correct option is (c).

14. V = 1000 cm3

Mass = 500 g

\ = = -Density g cm500

10000 5 3.


15. l = 6.3 mmV.C.D. = 31 M.S.D. = 1 mm, N = 10M.S.R. + V.C.D. × VC = 6.3

+ × =M.S.R. 31

106.3

∴ M.S.R. = 6.3 – 0.3 = 6 mmHence, the correct option is (b).

Assessment Test VI

1. Odometer is a device which is used to measure the distance covered by the vehicle.Hence, the correct option is (b).

2. =5− −1 km / h

18ms1 1

∴ = ×5

=− − −18km / h 1818

m s 5 m s1 1 1



3. If a body increases its velocity, then it will get the positive acceleration.Hence, the correct option is (b).

4. The slope v – t graph is acceleration.Hence, the correct option is (d).

5. The physical quantity which has only mag-nitude is called scalar and time has only magnitude.Hence, the correct option is (d).

6. A → a, B → c, C → b.Hence, the correct option is (a).

7. u = 0, a = 8 m s–2, t = 3 s

Distance traveled in 3 seconds = +ut at12

2

= + =012

(8)9 36 m.

Distance traveled in 2 s = × × =12

8 4 16 m

Distance traveled in third second = 20 m.Hence, the correct option is (c).

8.

W E

S

NC

B10 m

10 m

A

AB = 10 mBC = 10 mA is initial position.C is final position.So, total displacement is AL. By Pythagoras theorem

AC AB BC2 2= +

= + = =10 10 200 10 22 2 m

∴ Distance covered is = AB + AC = 10 + 10 = 20 mHence, the correct option is (a).

9.

7 m AB 7 m• • •

Displacement after 112

rotations is = 14 m

Time = 4 s

∴ Average velocity = = −144

3.5 m s 1


10.

45°

10 m

A

B C10

45°

Here, AB = height of the building

As ΔABC is right angled isoceless triangle,

i.e., ∠A = 45°, ∠C = 45° , ∠B = 90° then AB = BC

∴ BC = 10 m (AB = 10 m given)


11. 4 s 2 s

21

CBA

x• • •

I case : A → BLet initial velocity = u m s–1

T = 4 s; s = xSubstituting in former,

∴ = +s ut at12

2

x u x u= × + × × ⇒ = +412

32

16 4 12

x = 4 × 3 + 12 = 24

∴ x = 24 mHence, the correct option is (c).

12. Given v – t graph and graph in (2) option both shows uniform acceleration.Hence, the correct option is (b).


13. 3 sCBA

25 m d• • •

Case I: A → B

Here, car starts at A and reaches B after cover-ing 25m

u = 0; s = 25 m; t = 3 s

S = ut+1/2at2

25 0 312

9= × + × ×a

⇒ = −a509

m s and1 VB = u + at

= + × =0509

3503

∴ = −V503

m sB1

Case II: B → C

Here, u = =−V V503

m s , 0B1

=− −a

503

m s 2

SV u

ad=

−=

−

× −

2 22

2

2

0503

2509

50 503 3

950 2

25 m=− ×

××

− ×=


14. BP PB

Sbd• ••

Let t be the time after which he catches the bus then,SP = vt = 1.5 × 40 = 60 mThe distance traveled by the bus is

Sb = +012

0 05 40 2( . )( )

= ×1600

20 05.

= 40 Sp = d + Sb

60 = d + 40∴ d = 20 mHence, the correct option is (c).

15.

D20 m s–1

V

E

CB5 s 10 s t

AO

Total distance = Area under V – t graph

38012

OA AD AB AD12

BC EB= × + × + ×

t38012

5 20 10 2012

20⇒ = × × + × + × ×

⇒ 380 = 50 + 200 + 10t

⇒ 380 = 250 + 10t

⇒ 130 = 10t

⇒ t = 13 sHence, the correct option is (b).

CHAPTER 2

Dynamics

Assessment Test I

1. Let the dimensions of the rectangular lamina be length () and breadth (b). When the rec-tangular lamina is resting on the longer side, the height of centre of gravity (h) is equal to

half of its breadth

b2

. When the lamina is

rotated by 90° in the vertical plane, it is rest-

ing on the shorter side that is on the breadth. Then the height of centre of gravity (h’) is

equal to half of the length of the rectangle

2

. Then the difference in the h and h’ val-

ues gives the shift in the position of centre of gravity.Hence, the correct option is (a).

2. Let m be the mass of the body. Determine the change in velocity of the body, i.e (y – x) m s–1.

It takes ‘t’s to change the velocity. So, the rate

of change in velocity is y xt−

m s–2, which is

acceleration of the body.The product of mass and acceleration gives the magnitude of external force acting on the body. Hence, the correct option is (a).

3. (A) → b The frictional force between highly-polished surfaces in contact increases.

(B) → d Interaction between the protons and neutrons inside the nucleus is nuclear force.

(C) → a Centre of gravity of an annular ring lies out-side the body.

(D) → c

When a person standing in a swing, sits, the height of centre of gravity of the system decreases.Hence, the correct option is (c).

4. Work done is said to be negative when the dis-placement of a body is opposite in direction to the force. When a body is moving upwards the displacement is in the opposite direction to the gravitational force.Hence, the correct option is (a).

5. When a person swims, he pushes the water in backward direction and he moves in forward direction. So, A is incorrect. Action and reac-tion act on two different bodies, therefore, R is also incorrect.Hence, the correct option is (d).

6. F = ma. Here a is constant

∴ F1 = m1a and F2 = m2a

⇒ 6 = m1a and 4 = m2a

If ‘F’ is force on m1 + m2, then

F = (m1 + m2) a = m1a + m2a

= 6 + 4 = 10 NHence, the correct option is (d).

7. Astronauts on the Moon and a person experi-encing a reactional force feel their weight. But a person undergoing a free fall does not experi-ence his weight.Hence, the correct option is (a).

8. Momentum, P = mv

P1 = P2

m2 = m120

1001

A.12 Chapter 2 Dynamics

v2 = ? m1v1 = m2v2

⇒ v2 = m vm1 1

2

v2 = m v

m120100

1 1

1

v2 = v100120 1 = 0.83v1 = 83% of v1

∴ The velocity should be decreased by 17%.Hence, the correct option is (a).

9. According to the law of conservation of momentum,m1u1 + m2u2 = m1v1 + m2v2

But here v1 = u2, v2 = u1

Thus, m1u1 + m2u2 = m1u2 + m2u1

m1(u1 − u2) = m2(u1 − u2)⇒ m1 = m2


10. m = 200 g = 0.2 kgu = – 2 m s–1

v = 2 m s–1

t = 2 millisecond = 2 × 10–3 s

Wall

+ ve

– ve

F = ma, but,

av u

t2 (2)

2 104 10

22 10 m s3

33 2=

−=

−×

=×

×−−

∴ F = ma

= (0.2) (2 × 103) = 400 NHence, the correct option is (b).

11. Work done = Force × displacement = mg × h

Work done to lift up the body from ground on moon

= mgmoon × = = =hmg

6206

3.33 Jearth


12. 2 m2 m

G1

1 m

1 m

Length of diagonal = 1 1 22 2+ = m

∴ The required distance = 2

212

= m


13. According to the law of levers,effort × effort arm = load × load arm

Effort = load load arm

effort arm×

=× ×10 10 2

= 200 N.Hence, the correct option is (a).

14. Mechanical advantage of an inclined plane

=lengthheight

By Pythagoras theorem,

length = + =3 4 52 2 m .

Thus, mechanical advantage

= =Loadeffort

53

Effort = load × 3

5


= 5 10 35

× × = 30 N = 3 × 106 dyne


15.

Efficiency = Mechanical advantage

velocity ratio

From given figure,E = PL = 3PMechanical advantage

= = =LE

PP

33

The number of pulleys in the system are 3. Thus, the velocity ratio (V.R.) = 3.

Efficiency (η) = = =M.A.V.R.

33

1


Assessment Test II

1. Centre of gravity of an equilateral triangular lamina lies at its centroid. Divide the equilateral triangle into two right angle triangles by draw-ing a median on its base. Now find the height of the median using Pythagoras theorem. The centroid divides the median in the ratio 2 : 1, so by dividing the median in the same ratio find the lengths of the two parts. The length of the median from the base to the centroid give the height of the centre of gravity from the base of the triangle.Hence, the correct option is (d).

2. First of all the given load is in kg wt, convert it into newton by multiplying with g also convert the length of the crow bar into cm. The distance between the load and fulcrum is taken as load arm. By subtracting the load arm from the length of the crowbar, we will get the effort arm. Now substitute the load, load arm and effort arm in the law of levers, i.e., load × load arm = effort × effort arm. By solving the expression, we will get

effort = load load arm

effort arm×

.


3. A → dStreamlining of bodies minimizes the friction due to air when the bodies are moving with high velocities.B → eCentre of gravity of boomerang lies outside the body.C → aA cylindrical vessel resting on the curved sur-face is an example for neutral equilibrium.D → bCentre of gravity of a solid right circular cone resting on its base, lies within the body.Hence, the correct option is (b).

4. Work is defined as the product of force and dis-placement along the direction of force. As the force is perpendicular to the displacement, the work done is zero.Hence, the correct option is (a).

5. When a person steps out of a boat, the boat moves back. So, A is correct. The boat moves back due to the reaction force acting on the boat, where action is the motion of the person. So, R is the correct explanation for A.Hence, the correct option is (a).

6. Let the force be F; m1 and m2 be masses of 1st and 2nd bodies, respectively. a1 = 2 m s–2 and a2 = 6 m s–2

∴ F = m1a1 = m2a2 = ma


where, m = m1 + m2

m1 × m2

⇒ 3m2 = m1

∴ a = Fm

m am m

m am m

1 1

1 2

2 2

1 2

=+

=+

= mm m

mm

63

64

2

2 2

2

2

×−

= = 1.5 m s–2


7. Weightlessness is experienced in an artificial satellite. Artificial satellite is in a state of free fall with an acceleration equal to g. Hence, all bod-ies in the satellite experience free fall whereas on the Moon, the weight of the Moon is quiet large and is sufficient to produce gravitational attrac-tion and this produces the weight of the body.Hence, the correct option is (b).

8. 1st case:

mass = mvelocity = v∴ momentum, P1 = mv

2nd case:

Mass = 2m

velocity = v – v2

= v2

∴ momentum, P2 = (2m)v2

P2 = (2m) v2

= mv

P1 = P2. Therefore, there is no change in momentum.Hence, the correct option is (a).

9. According to the law of conservation of momentum,m1u1 + m2u2 = m1v1 + m2v2

⇒ m1u1 + m2u2 = (m1 + m2)v

The bodies A and B are moving in opposite directions. Let u1 be taken as positive, then u2 would be negative.

⇒ m1u1 – m2u2 = (m1 + m2)v

v can be positive if m1u1 > m2u2

Thus, the system will move in the direction of A if its momentum before collision is more than that of B before collision.Hence, the correct option is (d).

10. According to Newton’s second law of motion, force that acts on body A is

F = m v u

t( )−

= 5( 2 5)0.1 10 3

− −× − =

5 710 4

− ×−

= –35 × 10+ 4 N

According to Newton’s third law of motion, an action has equal and opposite reaction.

Thus, force exerted on body B by

A = 35 × 104 N


11. Mass, m = 1 kg.

Acceleration, a = −

=− −

−s

2 m s 0 m s1

2 m s1 1

2

Displacement, S = ut + at12

2

= (0) (5) + 12

(2) (5)2 = 25 m.

Work done, W = F × S = m × a × S= (1 kg) (2 m s–2) (25 m) = 50 JHence, the correct option is (a).

12. The volume of mercury remains same.

Area × height = Area × height

Let the height be h’ on transfering the mercury to a new vessel.

2A × h’ = A × h

h’ = A h

A2×

h’ = h2


The shift in CG = h h2 2-

’

= h h h2 4 4

− = = h4

m.


13. By the principle of lever,load × load arm = power × power arm

load = power power arm

load arm×

= 60 10 2.5

1.5× ×

= 1000 N

Mass object = 100010

= 100 kg


14. Velocity ratio (V.R) = number of pulleys in the system = 4.

Efficiency (n) = M.A.V.R.

where M.A. is the me-

chanical advantage.Given η = 80%

∴ M.A. = (η) (V.R.) = 80

100× 4 = 3.2


15. Mechanical advantage of an inclined plane

= lengthheight

= 12 5

5

2 2+ =

135

= 235


Assessment Test III

1. By polishing surfaces, by using lubricants and by using ball bearings we can reduce the friction.Hence, the correct option is (d).

2. The passengers being in a state of motion are not ready to stop suddenly. Hence, the correct option is (b).

3. Work done on the body is converted to its P.E. when it is lifted from surface of the earth. So, work = P.E. = mgh

= 5 × 10 × 50 = 2500 J

∴ work = 2500 J = 2.5 × 103 J


4. Given: Effort (E) = 25 N

Load (L) = 100 N

SE = displacement of effort = 0.25 m

= 25 cmDisplacement of load = 10 cm = SL

MA = LE

=10025

= 4

V.R = SESL

=25010

= 25

∴ efficiency of machines is

η =MAVR

=4

25=0.16

η = efficiency = 0.16% of efficiency = 0.16 × 100 = 16%Hence, the correct option is (d).

5. The lever in which effort is between load and fulcrum is called III-order lever. For forceps, effort lies between load and fulcrum. Hence, the correct option is (c).

6. 1 newton = 105 dyneHence, the correct option is (d).

7. The change in the momentum per unit time is equal to Force.

F = mv mu

t-( )


Mv – mv = F × t = 100 × 8 = 800Change in momentum 800 N sHence, the correct option is (b).

8. Given: mass(m) = 1000 kgHeight = (h) = 4 mTime = (t) = 1 min = 60 s

Power = worktime

= P Etime

. .

= mgh

t

= 1000 10 4

60× ×

= 4000

6

= 666.6∴ Power = 666.6 watts or = 0.7 kW Hence, the correct option is (a).

9. Newton’s first law is also known as law of iner-tia. Newton’s second law is F = ma. Recoil of a gun is an example for Newton’s third law.

10. Given: m1 = 1500 kgm2 = mu1 = 90 km h–1 = 25 m s–1

u2 = 0

v1 = v2 = 50 km h–1 =25018

According to the law of conservation of momentum,m1u1 + m2u2 = m1v1 + m2v2

1500 × 25 + m(0) = 1500 ×25018

+ m 25018

1500 × 25 = 25018

(1500 + m)

2700 = 1500 + m m = 2700 – 1500∴ m = 1200 kgHence, the correct option is (b).

11.

shift410

45

2

When length of the rod is height 0.1 C.G.

from the ground is 2

When 5

units is removed, new length is 45

units

Then new height of C.G. = 45 × 1

2 = 4

10

Shift of C.G is = 2

– 410

= 5 4

10 -

=

10 (or) 0.1 .


12. Figure for using the crow bar as a I order lever is given below:

block

L

E

F

Effort Arm = 100 cmLoad Arm = 114 – 100 = 14 cmLoad = 100 kg = 1000 NWe know that,Load × Load Arm = Effort × Effort ArmSubstitute above value,1000 × 14 = E × 100


⇒ E = 1000 14100

× = 140

E = 140 NOr E = 140 × 105 dyne Or E = 140 × 105 × 103 milli dyne Or E = 140 × 108 milli dyne Or E = 1.4 × 1010 milli dyne Hence, the correct option is (a).

13. Given:Load = 500 kg wt V.R = 0.9M.A = 5

Efficiency = M.AV.R

= 50.9

= 5.6

Effort = LM.A

= 5005

= 100 kg wtOr 1000 NOr = 108 dyne ∴ η = 5.6, E = 108 dyne Hence, the correct option is (b).

14. Given:

m = 1800 kg

u = 54 km h–1 = 15 m s–1

V = 0, s = 5 m

a = ?

a = −v us2

2 2

= 0 152 5

2 2−×

= 22510

−

Average force acting on it is,F = ma

= 1800 × 22510

−

= 40500∴ Force = 4 × 104 NHence, the correct option is (d).

15. Height of centre of gravity of solid cone is, h4

= 404

= 10 cm

Height of C.G. of solid cylinder resting on its

lateral surface is = 302

=15 cm

Difference in height of C.G. is = 15 cm – 10 cm = 5 cmHence, the correct option is (d).

Assessment Test IV

1. When lubricants are used between two sur-faces, a thin layer is formed between surfaces and friction is reduced. When we use ball bearings in machines, slid-ing motion is converted into rolling motion.Rolling friction is always less than sliding friction. Hence, the correct option is (d).

2. Inertia is measured by mass.Hence, the correct option is (b).

3. Given:M = 6 kgW = 4.8 × 109 erg = 4.8 × 109 × 10–7 J (1 erg = 10–7 J) = 4.8 × 102

= 480 J g = 10 m s–2 h =? w = mgh


480 = 6 × 10 × h

h = 4806 10×

h = 8 m∴ height = 8 mHence, the correct option is (a).

4. Given: Effort = (E) = 50 N Load (L) = WM.A = 2

∴ M.A = LE

2 = W50

W = 100 NHence, the correct option is (c).

5. For hand, Effort is between load and fulcrum.Hence, the correct option is (b).

6. Change in the momentum is called impulse. Therefore, the unit of momentum and change in the momentum is same.Hence, the correct option is (c).

7. Force applied on the body is equal to change in momentum in 1 s, i.e.,

F = change in momentum

time taken

F = 40010

= 40 N

= 40 × 105 dyne = 40 × 102 k dyne Hence, the correct option is (b).

8. Power = t

P.E

P = t

P.E

T = mgh

p

T = 2000 10 62000

× × = 60

∴ Time = 60 or 1 minHence, the correct option is (a).

9. P → r; Q → p; R → qA book resting on a surface is an example of balanced force. An apple falling down is an ex-ample of unbalanced force. Friction is a contact force.Hence, the correct option is (d).

10. Given:m1 = 1200 kgm2 = 1500 kg u1 = 72 km h–1 = 20 m s–1

u2 = 0, v1 = v2 = vAccording to law of conservation of momentum,m1u1 + m2u2 = m1v1 + m2v2

1200 × 20 + 1500 (0) = 1200v + 1500v

24000 = 2700v

v = 24027

= 8.9 ∴ Common velocity = 8.9 m s–1


11. Let intial length of the rod be , then its height

of C.G. is 2

When 14

th of the rod is removed, new length

is 34

Then new height of C.G is 34

× 12

= 38

Shift =2

– 38

= 5 ⇒ 4 3

8 -

= 5

⇒ 8

= 5

= 40So, original length = 40 cm = 0.4 mHence, the correct option is (c).

12. Given:Load = 1000 kg wt = 10000 NV.R = 20Efficiency = n = 90% = 0.9


Effort = E =?

η = MAVR

⇒ MA = η × V.R = 0.9 × 20 = 18II part,

E =L

MA=

10, 00018

= 5.6 × 102 N = 560 N


13. In the figure shown below, the crow bar acts as II-order lever.

Given, length of the crow bar = 120 cmEffort arm =120 cm (For minimum effort)Load arm = 30 cmI part:

M.A = Effort armLoad arm

=12030

= 4

II part:

For minimum effort,

E =L

M.A=

10004

= 250 N


14. I part

u = 40 km h–1 = 40 × 5

18 m s–1

F = 3.1 × 104 N; v = 0 ms–1; s = 4 m

a = −v u2s

2 2

=0 40

518

2 4

22

− ×

×

= 200 20018 18

− ××

×18

=−40, 000

2592

a = 4 102592

4− × m s–2

M = Fa

= 3.1 × 104 × 25924 104×

= 2008.8 kgMass of the car = 2009 kgHence, the correct option is (a).

15. When brick rests on its larger area then height

of C.G = 32

cm

When cylinder rests, on its circular plane area,

then height of C.G =2

cm

2

–32

= 15.5 (given)

– 3 = 31 = 34∴ Length of the rod = () = 34 cmHence, the correct option is (a).

Assessment Test I

1. Sound cannot travel through vacuum as it is a mechanical wave.Hence, the correct option is (a).

2. Ripples formed on the surface of water is a mechanical wave. A → sLight waves are non-mechanical waves. B → rCompressions and rarefactions are formed in a longitudinal wave. C → qCrests and troughs are formed on the surface of a transverse wave. D → pHence, the correct option is (b).

3. Velocitydistance

time=

(a) = = =Timedistancevelocity

1001500

115

s.

(b) Frequency = 100 Hz, wavelength λ = 2 m distance = 50 m

V f= × = × = 100 2distance

time

Timedistancevelocity

s= = =50200

14

.

(c) Time period = 2 s, number of oscillations = 50 Time taken for 50 oscillations = 50 × 2 = 100 s

(d) Distance between the sun and the earth = 1496 × 108 m Speed of light = 3 × 108 m s–1

Speeddistance

timetime

distancespeed

= ⇒ =

××

= ≈1496 10

3 10499 s 500 s

8

8

∴ The descending order of time is 500 s, 100 s, 14

115

s s,


4. Time period of a pendulum depends upon both length and acceleration due to gravity. When the weight of a body is changed without changing its mass, the value of ‘g’ also changes.Hence, the correct option is (b).

5. When the sound travels from one medium to another its frequency remains same.Hence, the correct option is (b).

6. Velocity of sound in solid (V1) > velocity in liquid

∴ >V

V1

2

1


7. The time period of a pendulum is independent of mass of the bob. Thus, time period = THence, the correct option is (a).

8. The time period of a pendulum is independent of amplitude provided amplitude is small.Hence, the correct option is (a).

9. λ λ= =f

TVelocity

λ λ= ⇒ = =2000.001

0.2 m 20 cm


10. f1 = n/2 = 2/1

TT

1

2

1

2

=

CHAPTER 3



ff1

2

2

1

= =

2 1

1

= 2

ff

21

2=

fn

2 2=

12

2

22T

nT

n= ⇒ =


11. Frequency = T1

Time period = 4 s ∴ frequency = 1/4 = 0.25 Hz


12. Among the waves, light has the highest velocity.Hence, the correct option is (d).

13. Distance travelled = velocity × time = v × tHence, the correct option is (b).

14. Velocity of a wave is independent of source.Hence, the correct option is (c).

15.

TT

1

2

1

2

=

T

T

T

TT T1

2

1

1

1

22 12

12

2= ⇒ = =

,

Frequency =1T

fT

fT2

21

1

1 1= ⇒ =

Tf22

1=

∴ = = =1

21

2122 1

21

f ff

f

T,


Assessment Test II

1. The speed of sound in a liquid is generally greater than that in a gas.Hence, the correct option is (a).

2. Velocity of a wave depends on medium; A → sFrequency of a wave depends on the source; B → r

Wavelength = Velocity

Frequency = Velocity × time

period; C → p

Frequency = number. of waves

time taken; D → q


3. (a) Frequency of the seconds pendulum = 12

= 0.5 Hz

(b) Frequency of rotation of the earth

= 1

24 60 60× × =

186 400, s

(c) Velocity = 340 m s–1, wavelength = 0.02 m.

Frequency = velocity

wavelength = 340

0.02 =

3402

× 102 = 17,000 Hz.

(d) Frequency = 1

Time period =

110 s

Therefore, the increasing order of frequ-

ency 186, 400

Hz; 1

10 Hz; 1

2 Hz; 17,000 Hz.


4. The frequency, f = 1Time Period

The time period depends on the length. Hence, the frequency depends on both time period and length of the pendulum.Hence, the correct option is (d).

A.22 Chapter 3 Wave Motion and Sound

5. When sound propagates through a medium, its amplitude changes.Hence, the correct option is (d).

6. Frequency is independent of medium ∴ ff1

2

= 1


7. T α

TT

1

2

1

2

= ; /2 = 2/1

T

T

T

TT T1

2

1

1

1

22 12

12

2= ⇒ = ⇒ =

T2 = 2 THence, the correct option is (b).

8. Frequency = 2 Hz

Time period = 12

= 0.5 s


9. Velocity = nλ330 = 10 × λ; λ = 33Distance between compression and rarefac-

tion = λ = =/ 233 m

216.5 m


10. Frequency = 20 Hz

= =Time period1

200.05 s.


11. Amplitude is the maximum displacement from the mean position. Amplitude = 20 cm.Hence, the correct option is (c).

12. To increase the frequency, the time period should be reduced and to reduce the time period, the length should be reduced.Hence, the correct option is (b).

13. Sound cannot travel through vacuum.Hence, the correct option is (d).

14. t = 50 s,

Frequency = = =numberof waves

timetaken10050

2 Hz


15. vv

1

2

=

ff1 1

2 2

But as the source is same f1 = f2

1 : 31

2

λλ

∴ =


Assessment Test III

1. Correct sequential order is ABCDE.Hence, the correct option is (b).

2. The distance between two successive troughs or crests is called wavelength (λ), then dis-tance between one crest to next trough is half

of the wavelength 2λ

So, here λ = 20 cm

2λ

= 10 cm.


3. Piccolo is flute type instrument.Hence, the correct option is (b).

4. A → c, B → d, C → b, D → a.Hence, the correct option is (a).

5. There are there important characteristics for sound to differentiate from one another, these are pitch, loudness and quality.Quality is also called timbre.If for two voices pitch and loudness are the same, by quality we can differentiate the voices. Hence, the correct option is (b).


6. By figure, we can say that time period of the wave is 4 sec, i.e., T = 4 s

f = T1

= 14

= 0.25

Frequency = 0.25 Hz.Hence, the correct option is (c).

7. GivenT1 = 2 × 10−3s; T2 = 5 × 10−3 sλ1 = λ, λ2 = λv1 = 2 m s−1 v2 = ?

v = Tλ

vv

1

2

= TT

1 2

2 1

λλ

××

v2

2

= 5 1020 10

3

3

λλ

× ×× ×

−

−

v2 = 8 m s–1

The ratio vv

1

2

= 28

= 14


8. λa = 2 m, λw = 1050 cm

Va = 340 m s–1, vw =?

f1 = f, f2 = f

V = fλ

v

vw

a

= w

a

λλ

vw = w

a

λλ

× va

= 10.5

2 × 340

vw = 1785 m s–1.


9. first node

first antinode

First end of thestring

λ = vf

= 330

1200 = 0.275 m

λ = 0.275 m

Distance of first node from first end of string

= 2λ

= 0.275

2 = 0.1375 m

Distance of first anti-node is

= 4λ

= 0.275

4 = 0.06875 m


10. l0 = 100 cm T0 = 2 s

l1 = 90 cm T1 =?

l3 = 105 cm T2 =?

T1 = 2π lg1

1

= 2π 90980

= 2π 998

T2 = 2π lg2

2

= 2π 105980

TT

1

2 =

2998

2105980

π

π


⇒ = ×T

T1

2

998

980105

⇒ = = =T

T1

2

90105

1821

67

.


11. For two sound waves in the given medium, frequency, amplitude and wavelength may be different but velocity is the same.Hence, the correct option is (b).

12. T = 2π g

Te = 2π ge

2 = 2π ge

22

= (∴

P2 = g)

/ = 1 mlength of the pendulum = 1 m = /

Tp = 2π gp

8 = 2π

xg

11

e×

4 = x11×

4 = x

x = 16.Hence, the correct option is (a).

13. v1 = vv2 = 1.5 v, v3 = 2.5 v

vv

1

2

= 1

2

λλ

λ2 = vv

2

1

λ1

= vv

1.5 × λ1

= 1.5 λ1

II Method

As ratio of % increase in velocities in two cas-es is 1 : 3, the % increase in wavelength also 1 : 3.∴ λ2 = 1.5 λ1

vv

1

3

= 1

3

λλ

λ3 = v

v3

1 λ1

= v

v2.5

λ1

= 2.5 λ1

∴ λ3 = 2.5 λ1

% increasing I case = 50%% increasing II case = 150%

Ratio = 50

150 =

13

.


14. Tm = 2π g

m

m

2 = 2

g16

m

e

2π

= 6 m

6 /m = /

/m = 16

The part of the length is removed

= / – 16

= 56

.



15. LL

1

2

= AA

1

2

2

=

3 mm4 mm

2

= 9

16.


Assessment Test IV

1. The correct sequential order is ACBD.Hence, the correct option is (d).

2. 2λ

= 12.5 cm

λ = 25 cm.Hence, the correct option is (b).

3. The instrument in which a membrane is excited at different places to produce different musical notes is called percussion instrument.Hence, the correct option is (d).

4. A → c, B → b, C → d, D → b.Hence, the correct option is (a).

5. Loudness of sound is directly proportional to amplitude of sound.Hence, the correct option is (b).

6.

Time period

2

amplitude

T = f1

= 12

= 0.5 s.


7. Given, f1 = 100 Hz, f2 = 100 Hz

T1 = 1

100 sec, T2 = 8 × 10−3 s

v1 = 3 m s−1 v2 =?

λ1 = λ, λ2 = λ

v = Tλ

vv

1

2

= TT

1 2

2 1

λλ

××

v3

2

= 8 10

1100

3λ

λ

× ×

×

−

v3

2 =

8 10 1001

3× ×−

v3

2

= 0.8

V2 = 3

0.8 =

308

m s−1

Ratio = vv

1

2

= 3308

= 31

× 830

= 45

.


8. V = f λ and when sound travels from one medium to another, there is no change in frequency.

v

vg

a

= g

a

λ

λ

vg = vg a

a

λ

λ.



9. 1st Antinode

Distance of I Anti-node from the fixed end is

= 4λ

and 4λ

= 2 m (given)

⇒ λ = 8 mV = f λ = 1000 × 8 = 8000 m s−1

Velocity of wave is = 8000 m s−1.Hence, the correct option is (a).

10. T0 = 100 cmT1 = 90 cmT2 = 90 + x

T1 = 2π lg1

1

= 2π g

90

T2 = 2π lg2

2

= 2π x

g90 +

TT

1

2

= g

xg

290

290

π

π +

TT

1

2

= x

9090 +

But TT

1

2

= 3 : 2 (given)

32

= x

9090 +

34

= x

9090 +

90 + x = 120 x = 120 – 90 x = 30 cm.Hence, the correct option is (c).

11. For a given sound wave, there is a change in wavelength and velocity when it travels from one medium to another but there is no change in frequency.Hence, the correct option is (a).

12. Te = 2π ge

4 = 2 ∵ g( )2Π =

L = 4 mHere we need not do anything with values of planet.Hence, the correct option is (d).

13. λ1 = λ, λ2 = 1.25 λ

vv

2

1

= 2

1

λλ

V2 = 2

1

λλ

× v1

= 1.25

1100λ

λ×

= 1375

v2 = 1375 m s–1


14. Te = 2π l

ge

e

5 = 2 l

ge

e

2π

52

= le

/e = 254

∴ = 6.25 mOn the planet,

Tp = 2π l

gp

p


5 = 2

g2p

p

2π

52

= l

2p

l

2p =

254

Lp = 12.5Change in length lp – le = 12.5 – 6.25 = 6.25 m.Hence, the correct option is (a).

15. A1 = A A2 = A120

100

L1 = L L2 =?

LL

2

1

= AA

2

1

2

⇒ L2 = AA

2

1

2

× L1

⇒ L2 =

AA

120100

2

× L

= 1.44 L L2 = 1.44LChange in loudness = L2 – L1

= 1.44L – L= 0.44 L

= 44

100= 44% L% change in loudness = 44%.Hence, the correct option is (d).

Assessment Test I

1. During the flow of heat energy, temperature may not always change and substance may not always change its state. A physical contact is not required for the flow of contact by radiation.Hence, the correct option is (d).

2. At the ice point, the Celsius scale has the low-est reading (0° C), hence, 20° C is the highest temperature.Hence, the correct option is (a).

3. −

=−K F

t313 273

10032

18

F = 104° FHence, the correct option is (b).

4. As the surrounding temperature is less than 0°C water converts to iceHence, the correct option is (a).

5. The mass of water is required to explain the processHence, the correct option is (c).

6. The direction of the flow of heat depend on temperature.Hence, the correct option is (d).

7. Temperature is the measure of hotness or cold-ness A → dHeat is a form of energy B→ aSpecific heat capacity does not depends on mass. C → cHeat capacity depends on mass.D → bHence, the correct option is (a).

8. Specific heat capacity of water is 1 cal g–1°C–1


9. The high specific heat capacity is the important property.Hence, the correct option is (a).

10. −

=−C4 2

80

100

C = 28

100× = 25° C.


11. At the top of a mountain, cooking is difficult as the pressure is less there.Hence, the correct option is (a).

12. Sea and land breeze are due to convection cur-rent of air. This is because during day time, land gets heated faster and during night land gets cooled faster.Hence, the correct option is (c).

13. As pressure increases, melting point of ice decreases. Hence, it is not possible to join two pieces of ice to single one.Hence, the correct option is (b).

14. (a) 100 = 10 × s × 10 s = 1 cal g–1°C–1

(b) 200 = 5 × s × 30

s = 200150

43

= cal g–1°C–1

(c) 4204 2.

= 50 × s × 5

s = 100250

25

= cal g–1°C–1

The increasing order is CBAHence, the correct option is (d).

CHAPTER 4

Heat


15. Q = m L

Latent heat (L) = Qm

=energymass


Assessment Test II

1. Temperature can also change when the heat flows in the form of radiation.Hence, the correct option is (d).

2. The number of divisions in the Celsius and Kelvin scales are the same and are the highest in the Fahrenheit scale. Hence, the DC = DK> DF Hence, the correct option is (b).

3. 122 32

1800

100−

=−C

C = 50°CTemperature of A = 60°C and that of B = 50°CHence, heat flows from A to B.Hence, the correct option is (a).

4. As the temperature of the substance is 110°C, some amount of water evaporates.Hence, the correct option is (c).

5. Q = m L

Q = 100 × 80 = 8000To melt the ice, 8000 cal of heat is required.Therefore, the resultant temperature is 0°CHence, the correct option is (a).

6. If their temperature is same, heat flows from one to another. If the temperature of the solid form is greater than that of the liquid form, it may melt.Hence, the correct option is (d).

7. Kelvin is the absolute scale of temperature A → bBimetallic strip works on the expansion of material on heating B → aRadiation requires no medium C → cConvection required medium D → dHence, the correct option is (b).

8. (A) Q = m LF = 10 × 80 = 80 cal(B) Q = m LV = 10 × 540 = 5400 cal

(C) Q = m S Dt = 10 × 1 × 100 = 1000 calThe increasing order of time is B C A.Hence, the correct option is (d).

9. Water is used for fermentation as it has a high specific heat capacity.Hence, the correct option is (a).

10. xx

410

12

−−

=

10 – x = 8 – 2x

x = 2 cmHence, the correct option is (b).

11. If humidity is high, water vapour condenses resulting in to rainfall.Hence, the correct option is (a).

12. As we move away from the surface of the earth, the temperature decreases as air is not heated by radiation.Hence, the correct option is (d).

13. The melting point of certain substances, like water, decreases with pressure. In the case of certain other substance, it increases with pres-sure. Boiling point water increases with the addition of impurity.Hence, the correct option is (b).

14. (A) C = Qt∆

=100

5= 20 cal°C–1

(B) C = 20030

203

= cal°C–1

(C) C = 40010

= 40 cal°C–1

∴ The increasing order is BACHence, the correct option is (b).

15. Q = m S Δt = C Δt

Heat capacity C = Q

t∆

= Energy

Change in temperature


A.30 Chapter 4 Heat

Assessment Test III

1. Mass Hence, the correct option is (d).

2. A → qB → sC → pD → rHence, the correct option is (c).

3. Steam at 100°C has more energy.Hence, the correct option is (b).

4. Conduction and convection mode transmis-sion of heat require a medium.Hence, the correct option is (d).

5. Less thermal transmission takes place on white and smooth surface.Hence, the correct option is (b).

6. Mw = 15 g; Tw = 100° C (hot)Mice = 15 g; Tice = 0°CTemperature of mixture (T) = ?Specific heat capacity of water = 1 cal g–1°C–1

Specific heat capacity of ice = 0.5 cal g–1°C–1

Heat lost by hot body = heat gained by cold body

mwsw(tw – x) = MiLi + mwsw(x – 0)15 × 1(100 – x) = 15 × 80 + 15 × 1(x – 0) 1500 – 15x = 1200 + 15x

300 = 30x

x = 10°CHence, the correct option is (c).

7. All of the above Hence, the correct option is (d).

8. QSRTPHence, the correct option is (c).

9. Heat lost by hot body = heat gained by cold body

Heat lost by hot bodyHeat gained by cold body

= 1 : 1


10. FC

= 3

C = ?

C = 100180

32F −( )

C = 59

3 32C −( )

C = 15

95 32

9C

−×

159

5 329

CC−

×=

C69

5 329

=×

C = 5 32

6803

×= °C


11. Specific latent heat of ice is 336 J g–1 = 3,36,000 J kg–1 = 80 cal g–1


12. P = 200 WM = 1000 g = 1 kgT1 = 35° C, Sw = 1 cal g–1°C–1 = 4200 J kg–1°C–1

T2 = ?P × t = m(T2 – T1)Sw

200 × 4.2 × 60 = 1 × 4200 × (T2 – 35)

∴ T2 = 200 4 2 604200

35× ×

+.

= 12 + 35 = 47°CHence, the correct option is (d).

13. SHg = 0.14 Jg–1°C–1

HHg = 140 J g–1°C–1

m = ?H = m. S

∴ m = HS

= =1400 14

100 01. .

= 1000 g = 1 kg



14. P = 20 Wm = 200 gt = 4 minP × t = mL

∴ L = Ptm

= 20 4 60200

× ×

= 24 J g–1


15. ms(T1 – T) = ms(T – T2)

T = T T1 2

2+


Assessment Test IV

1. Specific heat capacity is the property of the material and it is independent of all the given factors.Hence, the correct option is (a).

2. A → qB → sC → pD → rHence, the correct option is (b).

3. Substance at absolute zero temperature has less energy.Hence, the correct option is (a).

4. Radiation mode of transmission of heat does not require a medium.Hence, the correct option is (a).

5. Black surface Hence, the correct option is (a).

6. mw = 10 g; Thw = 60°C; T = 40°Cmcw = 15 g, Tcw = t1 = ?Sw = 1 cal g–1°C–1

Heat lost by hot body = heat gained by cold body

mw sw (Tw – T) = mw sw (T –Tcold water) 10 × 1 × (60 – 40) = 15 × 1 × (40 – t1) 10 × 20 = 15 × 1 × (40 – t1)

∴ t1 = 4020015

−

= 2403

× = 26.6°C


7. ∆ ∆ ∆C F K100 180 100

= =


8. SPQTRHence, the correct option is (c).

9. m × s (90 – T) = ms(T – 10)90 – T = T – 10

∴ T = 90 10

2+

= 50°C


10. CK

= 4 ; K = ?

C K100

273100

=−

4K = K – 273 3K = –273

∴ K = 2733

− = – 91 K


11. Specific latent heat of steam is 2260 J g–1 = 540 cal g–1


12. m = 100 g = 0.1 kgT1 = 20°C, sw = 4200 J kg–1°C–1

T2 = 80°CT = 2 min = 2 × 60 sP = ?

A.32 Chapter 4 Heat

P × t = ms (T2 – T1)

P = ms T T

t2 1−( )

= 0.1 4200 80 202 60

( )× × −×

= 4212

60×

= 210 WHence, the correct option is (b).

13. mcu = 0.120 kgScu = 100 cal g–1°C–1

H = ?H = ms

= 0.120 × 100 = 12 cal = 50.4 JHence, the correct option is (b).

14. Lf = 80 cal g–1

P = 25 W

m = 100 g

T = ?

t = mLP

= 0.1 80 4.2 1000

25 60× × ×

×= 22.4 min


15. ms(T1 – T) = ms(T – T2)

T = T T1 2

2+

T1 = 90° C , T2 = 30° C

∴ T = 90 30

2+

= 1202

T = 60° CHence, the correct option is (d).

CHAPTER 5

Light

Assessment Test I

1. 30°

d

At from the figure d = 180 – 60 = 120°Hence, the correct option is (c).

2. Image formed by a plane mirror is virtual Hence, the correct option is (c).

3. 360 3605

θ= =

72


4. When light ray travels from A to C, it undergoes reflection (T. I. R). Therefore, A is denser and C is rarer. No other conclusions can be made.∴ μA > μC


5. As the angle of refraction in medium C is greater than the angle of incidence in medium A, the correct relation is Vc > VA.


6. The refractive index of a prism is the highest for violet, and hence, the violet is deviated through the maximum extent.Hence, the correct option is (a).

7. Convex lens forms both virtual and real image.Hence, the correct option is (d).

8. As the object is moved closer to the lens, the magnification increases.Hence, the correct option is (a).

9. In this case, as the angle of refraction increases, the wavelength decreases.Hence, the correct option is (a).

10. Blue colour of the sky is due to the scattering of light. A → bMirages are formed due to total internal reflection. B → aTwinkling of stars is due to the refraction. C → dFormation of rainbow is due to the dispersion of light. D → c.Hence, the correct option is (a).

11. In Prism periscopes, total internal reflection take place.Hence, the correct option is (b).

12. m = 1 22

Sin C= =

VV

Sin C = 12


13. Height of the object = 5 cmf = 20 cm u = –30 cm

1 1f v u

= −1

120

1 130

= +v

= −−

=v

v1 1

201

3030 20

60060cm

1

Magnification = h

h=

vu

i

o ⇒ =

h

56030

i

hi = 10 cmHence, the correct option is (c).

14. Focal length = diameter of eye ball = fHence, the correct option is (a).

A.34 Chapter 5 Light

15. Thickness = 5 cm

μ = real thickness

apparent thickness

x32

5= ; x = 10

3

Shift = −=

−=

5 103

15 103

53

cm


Assessment Test II

1. Angle of deviation, d = 180 – 2i

= 180 – 2r; 90 = 180 – 2r

2r = 90; r = 45°Hence, the correct option is (a).

2. Image formed by convex mirror is virtual and diminished.Hence, the correct option is (b).

3. n = 9 = 360θ

θ = 3609

= 40

360θ

– 1 = 9 θ ⇒ θ = 36°


4. μP > μQ

∴ When a any light ray travels from Q to P, it undergoes refraction.Hence, the correct option is (c).

5. As the light ray travelling from P to Q and from Q to P bends towards the normal μR > mQ > mP.

∴ μR > μP


6. The velocity of red light entering a medium is more than the velocity of violet light.Hence, the time taken by the red light to trav-el through glass is less than that of violet.Hence, the correct option is (d).

7. A light ray passing through the optic centre is not diverged by a concave lens and a concave lens always forms virtual image.Hence, the correct option is (c).

8. The image becomes smaller and moves closer to the focus, when the object moves away from the convex mirror.Hence, the correct option is (d).

9. Refractive index, μ = 1

Sin C

So more the angle of refraction, more is the re-fractive index, and hence, less is the critical angle.Hence, the correct option is (d).

10. The total internal reflection is used in optic fibre communication. A → cThe swimming pool appears shallow due to the refraction of light. B → dImage is formed an a plane mirror due to reflection. C → aSky appears orange due to the scattering of light. D → b.Hence, the correct option is (a).

11. Refraction takes place in mirror periscopesHence, the correct option is (a).

12. m = 1

Sin C=

VVr

Vr = V Sin CHence, the correct option is (d).

13. Height of the object = 3 cmFocal length = 20 cmHeight of the image = 6 cm

hiho

vu

vu

vu

= =63

=12

=

u = 2v

1=

1 1f v u

−

120

1 12

120

2 12

= + =+

v v v;


V = 30 cmu = 60 cm; u + v = 90 cm.Hence, the correct option is (d).

14. As the focal length is less than the diameter of eye ball, the image is formed in front of the retina, and hence, the person is suffering from short sightedness Hence, the correct option is (a).

15. h = 30 cmaμw = 4/3

wμa = Real height

Apparent height

x34

30=

x = 40 mshift = 40 – 30 = 10 m.Hence, the correct option is (a).

Assessment Test III

1. Light is a form of energy that causes the sensa-tion of vision due to reflection. The formation of shadow is an example for rectilinear propaga-tion of light. Hence, the correct option is (d).

2. The point of intersection of reflected rays is a real image.Hence, the correct option is (b).

3. Light rays are converged by concave mirror.Hence, the correct option is (c).

4. 20 cm

20 cm

•

Image distance = – 20 cmHence, the correct option is (b).

5. f = – 30 cm,(Size of the image) = 3 (size of the object)

m = v

u−

= – 3

v = 3u

f1

= u1 +

v1

130−

= u

1−

+ u

13( )−

u1

301

113

= +

u1

301 4

3=

; u = 40 cm


6. Let the shift in position of the mirror = x∴ u1 = u – xV1 = (u + x) – 20But u1= V1

∴ u – x = (u + x) – 202x =20 ⇒ x = 10 cm


7. C = 3 × 108 m s–1

μ = cv

1.8 = v

3 108×; v =

3 101.8

8× = 1.67 × 108 m s–1


8. In this case, the light rays are converged behind the retina. Hence, the focal length is greater than that of a normal eye.Hence, the correct option is (c).

9. In the outer space, the sky appears dark as there is no atmosphere, and hence, light does not undergo scatteringHence, the correct option is (c).

A.36 Chapter 5 Light

10. Scattering – Blue colour of the sky.Total internal reflection – Sparkling of diamond.Refraction – Twinkling of stars.Reflection – Formation of image by a plane mirror.Hence, the correct option is (a).

11. (b) Place the concave mirror on a ‘V’ shaped stand.

(a) Focus the mirror to a distant object.(d) Adjust the position of the screen, such that

a clear image is formed on it.(c) Measure the distance between the screen

and the mirror.Hence, the correct option is (c).

12. Refractive index of lens = 32

Refractive index of medium = 52

As the light rays are entering from a denser medium to a rarer medium, they diverges after refraction.Hence, the correct option is (a).

13. Height of the image = 4 cm.Magnification = − 2

M = hh

I

o

– 2 = h4

o

⇒ ho = – 2 cm

The image formed is real and inverted as the magnification is negativeHence, the correct option is (a).

14.

60°

60°

60°30


15. μ = Real depth

Apparent depth

AD43

2 m=

A . D = 32

m.


Assessment Test IV

1. Image is formed due to both reflection and refraction of light.Hence, the correct option is (d).

2. The point of intersection of incident rays is called a real object.Hence, the correct option is (a).

3. Light rays are diverged by a concave lens. Hence, the correct option is (c).

4. Image distance = – 20 cmHence, the correct option is (d).

5. f = 20 cm ;

vu

= 13

; v = u3

u1

201

=−

+ u1

3

= u u1 3−

+

u1

[– 1 + 3] = 120

⇒ u2 = 1

20 ∴ u = 40 cm


6.

x

u

5 cm

u

u – 5 u – 5

O


Let x = shift in position of image∴ x = 2u – (2u – 10) x = 10 cmHence, the correct option is (b).

7. Vx = 108 m s–1

Vy = 1.5 × 108 m s–1

xμy = V

Vx

y= 10

1.5 101015

23

8

8×= =


8. The light rays are converged in front of the retina. Hence, the focal length is less than that of a normal eyeHence, the correct option is (b).

9. In the evening hours, the sky appears orange or red as light rays travel longer distance of higher wavelength of light.Hence, the correct option is (a).

10. Dispersion – Rainbow (d)Scattering – Red light is used as signal (c)Total internal reflection – mirage (a)Rectilinear propagation – pin hole camera (b)Hence, the correct option is (b)

11. (C) Place the lens on a stand.(A) Focus the lens to a distant object.(D) Adjust the position of the screen to obtain

a clear image on it.

(B) Measure the distance between the lens and the screen.


12. As the light rays are entering from a denser medium to rarer medium, they converge.Hence, the correct option is (b).

13. ho = 20 cm, m = + 3

m = h

hi

o

3 = h

20i

hi = 60 mThe image is virtual and erectHence, the correct option is (a).

14.

Angle of deviation = 180°Hence, the correct option is (c).

15. x3

2 4=

x = 6 cmHence, the correct option is (c).

Assessment Test I

1. When silk cloth and glass rod are rubbed with each other, the electrons flow from glass rod to cotton cloth. Because of this, the cotton cloth, due to excess of electrons, becomes negatively charged and glass rod, due to lack of electrons, becomes positively charged.Hence, the correct option is (d).

2. Here, body A is at higher potential when com-pared to body B. The positive charges flow from A to B. , i.e., conventional current flows from A to B or electronic current flows from B to A.Hence, the correct option is (d).

3. The current always prefers least resistance path

iqt

net

= =

Given, n = 1013; t = 1s, e = 1.6 × 10–19 C

⇒ =× × ×

= ×−

−i2 10 1 6 10

153 2 10

13 196.

.C

A


4. Pwt

EEt

= =

E E = P × t = 50 W × 20 × 30 h

= 30, 000 W-h

= 30 kW h = 30 units

Bill = 30 × 2.50 = ` 75 Hence, the correct option is (c).

5. In fig (c), silk thread is an insulator, so the cur-rent flows through the bulb.In fig (b), silver wire is a conductor so the cur-rent flows instead of bulb through the wire.In fig (a), the plug key is open In fig (d), the bulb is fused.Hence, the correct option is (c).

6. The number of electrons coming from the cell into the circuit is equal to the number of elec-trons entering into the cell from the circuit. Hence, the correct option is (d).

7. Mica sheets are placed on either side of the heating element because mica does not con-duct electricity but transfers the heat.Hence, the correct option is (a).

8. A → cUsually, chemical decomposition reaction occurs in electrolytes.B → dElectrolyte in Brchromate cell is K2Cr2O7 + H2SO4.C → bAll metallurgical applications work on chemi-cal effect of electricity.D → aElectrolyte in Leclanché cell is NH4Cl.Hence, the correct option is (c).

9. V = l1 a1 = l2 a2

Given, l1 = 2 l2

⇒ = =al a

la2

1 1

212

RR

l al a

la

al

R R//

2 2 41 4

1

2

1 1

2 2

2

1

1

22

1= = × = ⇒ =


10. = = = = =−Pwt

EEt

1500 J30 s

50 J s 50 watt1


11. Bulbs A and B are connected in series.Hence, the correct option is (c).

12. Carbon and zinc rods act as positive and nega-tive electrodes, respectively.Hence, the correct option is (a).

CHAPTER 6

Electricity


13. The principle of chemical effects of electricity is used in electroplating.Hence, the correct option is (b).

14. Given, Pfan = 100 W; Pbulb = 30 W; PWM = 120 WTime, t = 10 h (i)

PEt

= (ii)

E = p × t; Efans = 2 × 100 × 10 J;Ebulbs = 2 × 30 × 10 J and EWM = 1 × 120 × 10 J (iii)Etotal = Efans + Ebulbs + Ewn (iv)


15. Electric current, i = qt

et

=

Speed, v = distancetime

= rt

2π

t = rv

2π

∴ i = e

rv

evr2 2π π

= .


Assessment Test II

1. The electrons flow from fur to the ebonite rod.Hence, the correct option is (a).

2. The body is at lower potential when compared to the ground. So, the electrons flow from the body to the ground. The conventional current flows form the ground to the body.Hence, the correct option is (b).

3. The current prefers the least resistance path. So, current flows through PQRS instead of bulbs B1, B2 and B3


4. Pwt

EEt

= =

⇒ EE = P × t

The combined power of bulbs = P = 100 + 100 = 200 WTime, t = 10 × 30 = 300 hEE = 200 × 300 W-h = 60,000 W-h = 60 kW-h = 60 units Electrical Bill = 60 × 3 = 180Hence, the correct option is (c).

5. In fig (a), the silk thread is an insulator, so the current doesn’t flow through the bulb. So the bulb doesn’t glow.In fig (b), the current passes through the bulb so the bulb glows. In fig (c), the current pass-ing through the bulb is a copper wire. So, the bulb glows. Hence, the correct option is (d).

6. The current in solids is due to the drift of free electrons. Insulators have less number of free electrons.Hence, the correct option is (b).

7. A → bThe working principle behind the gold cover-ing is the chemical effect of electricityB → dIn a button cell, zinc acts as the anode.C → cThe unit of E.M.F is volt. D → aAn electric stove works on the principle of heating effect of electricity.Hence, the correct option is (b).

8. The space between the brass tube and the heat-ing element is filled with magnesium oxide or quartz sand which is a good conductor of heat but a bad conductor of electricity. Thus, protecting the person landing it from receiving an electric shock. Nichrome has high electrical resistance, and so, it is the most preferred material for the preparation of heating elements.Hence, the correct option is (c).

A.40 Chapter 6 Electricity

9. Given, lA : lB = 2 : 3

RR

la

al

23

23

49

A

B

A

A

B

B

= × = × =


10. Pwt

EEt

= = = = =−10 000300

33 3 33 31,. .

Js

J s watt .


11. Bulbs A, B are in series, Bulbs C and D are in series. The bulb E is parallel to bulbs A, B, C and D.Hence, the correct option is (c).

12. Powdered carbon in a dry cell enhances the flow charges through electrolyte and lead oxide plates or spongy lead are used as elec-trodes in a lead acid storage battery Hence, the correct option is (b).

13. A Daniel cell is divided into two equal portions by a porous membrane. Hence, the correct option is (a).

14. Etotal = 100 × 100 W; wfans = 100 × 60 W;

wTLS = 100 × 40 W → (B)

⇒ Total time, t = 30 × 10 = 300 h → (C)

P = t∈

→ (E)

E = P × t Ebulbs = 100 × 100 × 10 JEfans = 100 × 60 × 10 JETLS = 100 × 40 × 10 J → (A)ETotal = Ebulbs + Efans + ETLS → (D)Hence, the correct option is (c).

15. Electric current i = qt

= 2 1.6 10 2 101

19 19× × × ×− −

= 6.4 A. Hence, the correct option is (b).

Assessment Test III

1. SI unit of electromotive force is volt.Hence, the correct option is (b).

2. In an electric circuit, electrons always move from lower potential to higher potential or negative terminal to positive terminal.Hence, the correct option is (d).

3. A → P Dry cell emf is 1.5 VB → r Voltaic cell emf is 1.08 VC → q Bichromate cell emf is 2 VD → p Leclanche cell emf is 1.5 VHence, the correct option is (b).

4. EADBFC Hence, the correct option is (c).

5. The number of free electrons present in a cer-tain volume of silver are greater than the num-ber of free electrons present in the same vol-ume of aluminium. Hence, the correct option is (b).

6. Resistance is inversely proportional to square of radius of the wire. Electrostatic force depends on the medium between the two charges. Resistance is the property of the material that opposes the flow of charge. Hence, the correct option is (d).

7. Voltaic cell has defects like local action and polarization.Hence, the correct option is (b).

8. When a neutral body is brought in contact with a negatively charged body, then it becomes negatively charged. Hence, the correct option is (b).

9. i = 5 At = 2 min, e = charge of an electron = 1.6 × 10 –19 Ct = 2 × 60 second


i = Qt

net

=

n = ite

= 5 2 601.6 10 19

× ×× −

= 375 × 1019 electrons

= 3.75 × 1021


10. P = 60 Wt = 20 hEnergy = ?

Power = energy

time

Energy = p × t = 60 W × 20 h = 1200 W h = 1.2 kW h = 1.2 Unit (∴ 1 kW h = 1unit)Hence, the correct option is (c).

11. N = 50 × 1018 electrons (gains) Q = ?Q = ±ne = –50 × 1018 × 1.6 × 10–19

= –8 CHence, the correct option is (d).

12. P = 60 WT = 10 hr

1 unit cost = ` 4In February month maximum days are 29-.E = p × t = 60 × 10 W-h per day = 600 × 29 W-h per month = 17400 W-hE = 17.4 kW-hTotal cost per month = 17.4 × 4 = ` 69.6/- ≈ ` 70.Hence, the correct option is (b).

13. L1 = ; r1 = r; R1 = RL2 = 2 ; r2 = 2r

RR

rr

2

1

2

1

1

2

2

= ×

R2 =

Rrr

22

1

1

2

×

R2 = R2


14. ρ

ρ= = =

×=

RR

A

A

r Ar A

rr

14

1

2

1

1

2

2

1 2

2 1

1 22

2 12


15. 2 Ω

2 Ω 2 Ω

2 Ω

2 Ω

2 Ω

2 Ω

1 Ω 1 Ω 4/5 Ω

9/5 Ω

2 Ω

A D 4 Ω⇒ ⇒ ⇒

Total potential, (V) = 20 V

Total resistance of the circuit = R = 95

Ω

Total current, (i) = VR

20 59

1009

=×

=

= 11.11 A.


A.42 Chapter 6 Electricity

Assessment Test IV

1. SI unit of an electric charge is coulomb.Hence, the correct option is (c).

2. Inside a cell, the conventional current flows from lower potential to higher potential or neg-ative terminal to positive terminal.Hence, the correct option is (d).

3. A → rB → pC → sD → qHence, the correct option is (d).

4. CBDAHence, the correct option is (b).

5. The number of electrons per unit volume is more iron.Hence, the correct option is (c).

6. Charge density is the ratio of charge and sur-face area. Carbon is not used as positive electrode in lead-acid storage battery.Polarization and local action are the defects of voltaic cell.Hence, the correct option is (d).

7. Dry cell and Leclanche cell have ammonium chloride as an electrolyte.Hence, the correct option is (d).

8. When a neutral body is brought closer to a negatively-charged body, then it becomes posi-tively charged. Hence, the correct option is (c).

9. P = 40 WR = 10 Ωi = ?t = 1 sP = i2R

i = PR

1/2

= 4010

1/2

= 2 A


10. E = 4,000 JT = 50 sP = ?

P = Et

400050

= = 80 W


11. N = 125 × 1018 electrons lost Q = +ne = +125 × 1018 × 1.6 × 10–19

= +20 CHence, the correct option is (a).

12. P = 40 WT = 15 h per day Total bill = ` 200/-Cost of 1 unit = ` 5/-

P = Et

E = P × tTotal cost = 1 unit cos t × E

E = 2005

= 40 kW-h = 40 unit


13. 1 = 2; r1 ≠ r2

RR

19

1

2

= ; r2 = ?

RR

rr

1

2

1

2

2

1

2

=

RR

rr

1

2

2

1=

r2 = rRR1

1

2

= r191


ç = r r3 31 =


14.

1

2

1

2

11

12

æ

èç

ö

ø÷ = =.

rr

∴

RR

rr

11

21

4 : 11

2

1

2

2

1

2 2

=

= ×

=


15. RAB = 2R

RCD = R2

VV

iRiR

RR

2

2

41

AB

CD

1

2

= = =


CHAPTER 7

Magnetism and Our Universe

Assessment Test I

1. Only direct current is used for the electrical method of magnetization. Alternating current diamagnetize the magnet.Hence, the correct option is (d).

2. (A) Keep a steel bar to be magnetized on a wooden table

(B) Take a strong permanent magnet and bring one pole (say north pole) of the magnet near one end of the steel bar and gently rub from one end to the other.

(C) Once it has reached the other end, lift the magnet gently away from the steel bar and again bring it to the starting end.

(D) Repeat this process several times so that the steel bar will be magnetized with the starting end as the north pole and the other end as the south pole.


3. A substance which is feebly repelled by a mag-net is a diamagnetic substance Hence, the correct option is (a).

4. The equatorial meridian of a magnet bisects the magnetic axis perpendicularly.Hence, the correct option is (a).

5. (a) Like poles repel each other.

(b) Unlike poles attract each other.

(c) Resultant magnetic field is zero.

(d) Magnetic field lines passing perpendicular to a given area is called magnetic flux.


6. If magnetic field lines intersect at a point, then there will be two directions for a magnetic field at a point which is impossible.Hence, the correct option is (a).

7. Magnetic lines of force energy emerge from the north pole and terminate at the south pole. So, A and B both are north poles.Hence, the correct option is (b).

8. Magnetic field lines are:

(i) closed, continuous curves.

(ii) directed from the north pole to the south pole outside the magnet and south pole to the north pole inside the magnet.


9. Magnetic induction depends on the strength of inducing magnet and the nature of the mag-netic substance.Hence, the correct option is (d).

10. In the Sun, hydrogen is converted into helium.Hence, the correct option is (a).

11. Distance travelled by light in one year is called a light year.1ly = 3 × 108 m s–1 × 365 × 24 × 60 × 60 = 9.46 × 1015 m.Hence, the correct option is (a).

12. The angle of declination is variable.Hence, the correct option is (c).

13. (A) Write the given values of magnetic moment (M) and magnetic length (2l) of the bar magnets A and B.

(B) Write the expression for pole strength (m)

for each magnet using, mM

=2

(C) Divide the two expressions to get the ratio of mA to mB.


14. When a magnet is broken into any number of parts, each part will have both the poles.Hence, the correct option is (c)


. 15. For a current carrying conductor, no magnetic poles exist.Hence, the correct option is (a).

Assessment Test II

1. When an iron piece is magnetized, all the mole-cules align themselves in the direction of external magnetic field by breaking their closed-molecu-lar chains, therefore, its length slightly increases.Hence, the correct option is (a).

2. (A) Draw a line in the middle of a white paper fixed on a drawing board.

(B) Place a bar magnet NS on the line such that its axial line coincides with the line on the paper and mark its boundary.

(C) Take a plotting compass and place it near the pole and mark the point 1 in the direc-tion in which the north pole of the plotting compass points.

(D) Repeat the procedure by shifting the com-pass and plot the points 2, 3, 4, etc.

(E) Join the points 1, 2, 3……. by a smooth curve.


3. Gold is a diamagnetic substance.Hence, the correct option is (c).

4. Physical length of a bar magnet is greater than the magnetic length.Hence, the correct option is (b).

5. (a) Region in space where the effect of a mag-net is felt is called magnetic field.

(b) Magnetic lines of force never intersect each other.

(c) A line joining the places of same angle of declination is called isogonic line.

(d) A line joining the places where the angle of dip is zero is called aclinic line.


6. Steel is used for making a permanent magnet, since its retentivity is high.Hence, the correct option is (a).

7. Magnetic lines of force emanate at the north pole and terminate at the southpole.Hence, the correct option is (c).

8. Repulsion is the sure test for magnetism.Hence, the correct option is (c).

9. Distance travelled by light in one year is called a Light year.Hence, the correct option is (c).

10. V = 3 × 108 m s–1

t = (8 × 60) + 20 = 480 + 20 = 500 SS = V × t = 3 × 108 m s–1 × 500 s = 15 × 1010 m.Hence, the correct option is (c).

11. The angle made by the Earth’s magnetic field with its horizontal component is called angle of dip.Hence, the correct option is (b).

12. (B) Write the given value of pole strength ‘m’ of the magnet.

(C) Find the value of length ‘l’ of the magnet from the problem and convert it into SI Unit.

(D) Write the required formula, magnetic moment (M) = m × 2l

(A) Substitute the values in the above formula to get the value of M.


13. Magnetic keepers used to prevent loss of mag-netism will be made of soft iron.Hence, the correct option is (c).

14. When a small steel rod is brought near a bar magnet, magnetism is induced in the steel rod and it gets attracted to the magnet.Hence, the correct option is (a).

15. The meteors seldom reach the Earth because of vapourization caused when they pass through the atmosphere.Hence, the correct option is (d).

A.46 Chapter 7 Magnetism and Our Universe

Assessment Test III

1. In our solar system, the planet Mercury has high orbital speed because speed is inversely proportional to the square root of radius of the orbit.Hence, the correct option is (c).

2. Shoemaker levy is a comet, remaining options are natural satellites.Hence, the correct option is (b).

3. Steel bar has high retentivity.Hence, the correct option is (b).

4. A → c SI. unit of pole strength is A–m. B → d Magnetic keeper prevents loss of magnetism. C → a SI unit of magnetic moment is A–m2. D → b SI unit of magnetic field induction is tesla. Hence, the correct option is (c).

5. BCDA (B) Keep the steel bar to be magnetized inside a

long coil of insulated copper wire. (C) Pass a direct current through the coil for

sometime. (D) The specimen of steel bar will get

magnetized. (A) The end at which current enters in an anti-

clock wise direction will become the north pole and the other end becomes the south pole.


6. DABCEHence, the correct option is (b).

7. Synodic month is of 2912

days from one new

moon to the next new moon.Hence, the correct option is (a).

8. Water is feebly repelled by a magnet because it is a diamagnetic substance. Hence, the correct option is (a).

9. Ewing’s molecular theory explained saturation of magnetism and the existence of dipoles. Hence, the correct option is (a).

10. Angle of inclination always varies from 0° to 90°.Hence, the correct option is (b).

11. The strength of a magnetic flux density increases as the magnetic strength increases and also the number of magnetic lines of force passing through a given area increases.Hence, the correct option is (d).

12. Net magnetic field induction is zero at point A i.e., it is a neutral point.Hence, the correct option is (c).

13. Venus is the planet that rotates from east to west direction. Hence, the correct option is (a).

14. Pole strength (m) = 2 × 10–2A–mEffective length (2) = 8 cm = 8 × 10–2 mMagnetic moment (m) =?M = 2 m = 8 × 10–2 × 2 × 10–2

= 16 × 10–4 A – m2

= 1.6 × 10–3 A – m2.Hence, the correct option is (b).

15. Orbit height of a geostationary satellite is 36,000 km. Hence, the correct option is (b).

Assessment Test IV

1. Among the following, Neptune has the mini-mum orbital speed because its orbit radius is maximum.Hence, the correct option is (d).

2. Saturn, Uranus, Jupiter and Neptune are Jovian planets.Hence, the correct option is (d).

3. Retentivity means retaining magnetism in the absence of applied magnetic field.Hence, the correct option is (b).


4. A → c → Saturn is a Jovian planet . B → d → Espionage means spying the movement of enemy. C → b → Steel can be made as permanent magnet. D → a → Soft iron can be made as electromagnet. Hence, the correct option is (b).

5. CADB

(C) Write the given value of pole strength ‘m’ of the magnet

(A) Note down the value of length ‘l’ of the magnet from the problem and convert it into SI unit

(D) Write the formula, magnetic moment ‘m’ = m2l

(B) Substitute the values in the above formula to get the value of M.


6. The increasing order of orbital speed is Jupiter, Mars, Earth and Venus.Hence, the correct option is (d).

7. 2912

is the average time gap between one full

moon and the next full moon. Hence, the correct option is (c).

8. As cobalt is a ferromagenetic substance, so it is strongly attracted toward magnet.Hence, the correct option is (b).

9. Ewing’s molecular theory explained the satu-ration of magnetism, directionally and attrac-tive or repulsive nature of magnetic poles.Hence, the correct option is (d).

10. Angle of inclination is the angle made by the Earth's magnetic field with its horizontal component.Hence, the correct option is (a).

11. The magnetic force between two poles is directly proportional to the product of their pole strengths and inversely proportional to the square of the distance between the poles. Hence, the correct option is (d).

12. The points B and C have the approximately similar magnetic field strength.Hence, the correct option is (b).

13. Constellation Orion is also called canis major.Hence, the correct option is (c).

14. Magnetic moment = 2 m

N S N S

Equatorial lineMagnetic moment of each piece

= = =M l m

l m2

22


15. Time period of a geostationary satellite is 24 hr, i.e., one mean solar day.Hence, the correct option is (d).

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