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10 th International Junior Science Olympiad,

Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

(i) The magnitude of the gravitational force experienced by the mass at a depth

from the surface (see figure) will be

[0.5]

(A) (B)

(C) (D)

Correct answer: (A) [0.5]

g(r) = GM(r)/r2 M(r) = (4/3)r3 = M /(4/3)R3

g(r) = (GM/R2)(r/R) = gr/R F = [mg/R]r = mg(1-h/R)

(ii) In the grid provided on your answer sheet, plot a graph of , where

is the force on the mass at a distance from the centre of the Moon, as a

function of , as varies from 0 to .

[1.0]

(iii) If kg, what is the minimum time (in seconds) it will take, from the

moment the mass is dropped through the hole at the surface, for it to reach the

centre of the Moon?

1

r/R

F/mg

(0,0) 1 2

0.25


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

[1.0]

Correct answer: T = 1619 s [1.0]

Substitute mg/R as k in the formula for the frequency, Time period = 6476

s, time take to reach the centre = 1619 s.

0 = 1/2(k/m)0.5

Time taken to reach the centre, T = 2(m/k)0.5

T = (R/g)0.5 T = 1619 s

(iv) The oxygen molecule O2 has a force constant, N m-1

. The equilibrium

bond length is m and the change in the bond length when it is

fully stretched is 6.0% of . Calculate the vibrational energy, that is the sum of

kinetic and potential energies per mole of oxygen (in kJ-mol-1

).

[1.5]

(Avogadro's number, NA = 6.0231023

)

Vibrational energy per mole = UN0 = 28.052 kJ/mole [1.5] Ls = 1.59 x 10-10 m [0.5]

Vibration energy is the work done in changing the separation from

equilibrium position to the fully stretched position [1.0].

Force, F = k(Ls-L) Work, W = 0.5k(Ls-L)2

U = 0.5k(Ls-L)2

Vibrational energy per mole = UN0 = 28.052 kJ/mole [0.5]

(v) The atomic weights of the halogen elements listed in the periodic table are:

F Cl Br I

19.0 35.5 79.9 126.9


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

Two halogen elements, X and Y, form diatomic molecules X2 and Y2 with force

constants N-m-1

and N-m-1

respectively. The vibration

frequencies are measured to be Hz and Hz.

Identify the halogen elements X and Y by writing their symbols. Write your

answer in the form X = , Y = in the answer sheets.

[1.0]

Correct answer: X = Cl and Y = F [1.0]

The ratio of the vibration frequencies is 0.623.Only X = Cl and Y = F are

the elements such that the ratio of the square roots of the masses

(my/mx)0.5 ~ 0.64.

Question 2

(i) If sunlight is shone through a transparent container (with walls of negligible

thickness) filled with nitrogen gas, what will be the ratio of the scattered light

intensity for colours corresponding to wavelengths 400 nm and 650 nm

respectively? [1.0]

Ratio of the scattered intensities = 6.2 [1.0]

Correct ratio of the light intensity = 0.9 [0.5] or

Correct ratio of the scattered light intensity without taking into account

solar spectrum [0.5].

The ratio of the intensity of 400 nm and 650 nm light in the sunlight is 0.9.

s(400)/s(650) = (650/400)4*0.9 = 6.2 [0.5].

Visibility range for polluted air 60 x 103 m or 75 x 103 m [1.5]


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

Scattering losses due to the pollutants will be proportional to 0.1*40 = 4

times larger compared to pure air. [0.5]

Pollutants act as additional scattering hence the visibility range reduces by

5 times (60 x 103 m)

(ii) Milk is a colloidal solution in which droplets of liquid

fat, of size around 100 nm, are suspended in water.

These droplets scatter light more strongly than the water

molecules, causing normal milk to appear white rather

than transparent.

Consider the following experiment. A few drops of milk

are added to a glass of water illuminated from above by

a beam of sunlight, as shown in the figure on the right.

The water turns cloudy, but some sunlight still passes through, since the

concentration of milk is small. The glass is now viewed (I) from below, and (II)

from the side, as shown in the figure.

When compared to the emerging light viewed from below (I), the emerging light

viewed from the side (II) will appear [0.5]

(A) bluish (B) orange (C) reddish (D) the same


Shorter wavelengths are scattered much more than the longer

wavelengths, hence blue will be scattered more along the direction (II)

compared to direction (I)

II

I


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

(iii) Which of the following atmospheric phenomena is mainly governed by Mie

scattering of light?

[0.5]

Images taken from:

(A) http://bostern.wordpress.com (B) http://www.kaneva.com

(A) red sunset (B) white clouds

(C) blue sky (D) rainbow


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

(C) http://lisathatcher.wordpress.com (D) http://www.freefoto.com

Correct answer: (B) white clouds [0.5]

(a) and (c) are due to Rayleigh scattering (wavelength dependent), (d) is due to

wavelength dependent refraction and dispersion through water droplets.

(i) The green colour of leaves and shoots of plants is usually due to the presence of

chlorophyll, the compound mainly responsible for photosynthesis. Which of the

following graphs depicts the correct absorbance spectrum of chlorophyll?

[1.0]

Correct answer: (B) [1.0]

For green colour the absorption is minimum and hence is reflected or

scattered the most

(ii) Assuming that the rate of photosynthesis is proportional to the amount of light

absorbed (see above figure), what will be the wavelength (in nm) corresponding to

the maximum photosynthesis rate in green plants?

[0.5]

450 nm [0.5]

Maximum absorption in Fig. b is at 450 nm.

[1.0]


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30


Larger absorbance where the solar spectrum has a maximum intensity.

Question 3

(a) The dissociation of in blood occurs in two steps. Write down balanced equations

for these two steps.

[0.5]

H2CO3 (aq.) H +(aq.) + HCO3- (aq.) [0.25]

HCO3- (aq.) H +(aq.) + CO3

2-(aq.) [0.25]

(i) Calculate the concentration of in a solution at 37 0C, and hence its pH value, if

and are present in equal concentrations in mol/l in that solution.

[0.5]

[H2CO3] = [HCO3-] K1 = [H

+]

[H+] = 2.2 ×10

-4 M [0.25]

pH = 3.65 [0.25]

(ii)

[1.0]


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

pH = 7.4 [H+]=3.98 × 10 -8 [0.5]

[0.5]

(b) Usually in the human body, is in equilibrium with the dissolved in the blood.

At 370 C, 5.0 x 10

-3.

Calculate the total equilibrium constant, for the reaction

[0.5]

[0.5]

(c) Blood plasma contains a total carbonate buffer pool, which is a mixture of and

with a total concentration of M at 38 0C. At this temperature the value

of the equilibrium constant is . The concentration of the is


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

negligible. Calculate the ratio of concentrations of and , and

their individual concentrations, in this blood sample at pH 7.4.

[1.5]

pH = 7.4 [H+]=3.98 × 10 -8

or [0.5]

[0.5]

[0.5]

Question 4

.

(a) Which of the above carry de-oxygenated blood?

[1.0]

1,4,5, RA and RV

(b)

[0.5]

What would be the individual’s heart rate (in beats/minute) as calculated from the table?


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

Heart rate: 60/0.7 = 85.7 beats/min [0.5]

(c)

[1.5]

(d) Blood flows from the heart into the aorta during a cardiac cycle. If the diameter of the aorta

is approximately 2.4 cm, then, using the table in 4(b) calculate the average speed (in

cm s-1

) of blood flowing into the aorta in one full cardiac cycle.

[1.0]

Speed = Volume/(cycle time*Area) [0.5]

Speed = 42/4.52 = 60/4.52

Speed = 13.26 cm/s (for cycle time of 0.7 s) or 23.23. cm/s (for cycle time of 0.4 s)

[0.5]

(e) Blood flows from the aorta and its major arteries into arterioles and fine-walled capillaries.

If all the major arteries in the body have a total cross-sectional area of about 7.0 cm2

calculate the average speed (in cm-s-1

) in the major arteries which have the same volume

of blood as the aorta flowing through them. [0.5]

V2 = 8.56 cm/s (13.26 cm/s), V2 = 14.99 cm/s (23.23 cm/s)

A1V1 = A2V2

FULL [0.5] Credits to be given for the correct value.

HALF [0.25] Credits to be given for the formula even if the value is wrong.

Time Mitral valve Aortic valve

0.2 s C O

0.6 s O C


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

[1.0]

Question 5

(i) Calculate the average acceleration of this cheetah required to reach its maximum

speed.

[0.5]

Average acceleration, [0.25]

[0.25]

(ii) Calculate the distance travelled during the first 3.0 s, assuming that the

acceleration is uniform.

[0.5]

Distance travelled during the acceleration phase , [0.25]

[0.25]

(iii) The cheetah has to do work against friction, mostly due to air. Assume that this

frictional force is always 100 N. Calculate the total mechanical work done by the

Aorta Renal

vein

Alveolar

space in

lungs

Pulmonary

artery

Y X Y X


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

cheetah during the first 23.0 s of its motion.

[1.0]

Work done in

Change in kinetic energy, [0.25]

[0.25]

Overcoming friction due to air, [0.25]

Total work done

[0.25]

(a) During the first 23.0 s, the body temperature of the cheetah rises from 38.5 0C to 40.0

0C. Take the specific heat of the body of the cheetah to be 4.2 kJ kg

-1 K

-1.

(vi) If the rise in body temperature is linear during this time, calculate the total heat

generated by the cheetah’s metabolism. Neglect any heat loss to the surroundings.

[1.0]

Heat generated in the body of the Cheetah, [0.5]

[0.5]

(vii) Assume that some of the energy generated by the cheetah’s body increases its

temperature and the rest corresponds to the mechanical work done. Calculate the

fraction of the total generated energy that is converted to kinetic energy.

[1.0]

Total energy generated in the body of Cheetah, [0.5]

Fraction = = 0.06 [0.5]


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

(viii) Write down the balanced chemical reaction for aerobic respiration.

[1.0]

The balanced reaction:

(ix) If the cheetah requires 400 kJ of energy, calculate the volume of oxygen required

if all this energy is to be obtained by aerobic respiration. Take the molar volume

of oxygen gas to be 24.5 litres.

[1.0]

Number of glucose molecules required to produce 400kJ of energy is

[0.25]

Number of mol of is

[0.25]

Volume of required, [0.5]

(x) The cheetah extracts oxygen from the air while breathing. The inhaled air (about

500 ml per breath) contains 20.0 % oxygen (by volume), while the exhaled air is

assumed to contain 15.0 % oxygen (by volume). Calculate the volume of oxygen

that the cheetah can use during the 23.0 s of its run, at a breathing rate of 150

breaths per minute.

[1.0]

Amount of absorbed by the lungs per breath is

[0.5]

Total number of breaths during its entire motion,


Pune, India

Theory Questions

Time : 3 hrs

Marks : 30

[0.25]

Thus the amount of intake of , [0.25]

(xi) Anaerobic respiration converts the energy from glucose into ATP. If glucose were

to be completely burnt up, one mole would release 2872 kJ of energy. What is the

efficiency of anaerobic respiration compared to complete combustion of glucose?

[1.0]

Energy generated in production of one mol of ATP due to oxidation of glucose is

[0.5]

Efficiency of the anaerobic respiration, [0.25]

[0.25]

(xii) If all the 400 kJ required by the cheetah for its run were to be produced by

anaerobic respiration, calculate the total amount of glucose (in kg) that would be

required.

[1.5]

Amount of glucose of required,

[0.5]

Approximate molecular mass of glucose,

[0.5]

[0.5]

10 th

International Junior Science Olympiad, Pune, India

Experimental Tasks

Page 1

Time : 3 hrs

Marks :40 A B C + +

Task: This task is divided into three parts. Total marks: 14

A1: To determine the centre of gravity of a triangular plate, A.

A2: To record the time period of oscillation for different

suspension points for the plate.

A3: To analyze the above data and results.

A.Q1 Determination of CG: [1.0 mark]

Mark “X” on Sheet 1 at the appropriate position to denote the CG (large sized sheet).

CG within 5 mm [1.0]

CG within 10 mm [0.5]

A.Q2 Table A.1: Oscillation measurements: [4.0 marks]

h

(m)

h2

(m2)

Time taken for 50 oscillations (s) T = T1/50

(s)

T2

(s2)

hT2

(ms2)

1st

(t1)

2nd

(t2)

3rd

(t3)

Mean (T1)

(t1+t2+t3)/3

H1 0.243 53.65

H2 0.155 47.77

H3 0.179 49.08

H4 0.098 45.48

For each value of h within ±5 mm [0.25 x 4.0= 1.0]

For each value of T1 within ± 1 s [0.5 x 4.0= 2.0]

For each value of T1 within ± 2 s [0.25 x 4.0= 1.0]

For calculating h2 and hT

2 [0.25 x 4.0= 1.0]

A

10 th


Experimental Tasks

Page 2

Time : 3 hrs

Marks :40 A B C + +

A.Q3Results of the data analysis

(a) Grid1: hT

2 (y-axis) versus h

2 (x-axis) [2.0 marks]

0.000.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

hT

2 (

m s

2)

h2 (m

2)

Grid 1

Plotting 4 points correctly [0.25 x 4.0= 1.0]

For best fit straight line [1.0]

10 th


Experimental Tasks

Page 3

Time : 3 hrs

Marks :40 A B C + +

A.Q4Table A.2: Calculations from Grid 1 [3.0 marks]

Quantity Numerical

value

FULL

CREDITS

HALF

CREDI

TS

Slope of the graph (s) 4.06 ± 0.2 [0.5] 4.06 ± 0.4 [0.25]

y-intercept of the graph (c) 0.040 ± 0.005 [0.5] 0.040 ± 0.01 [0.25]

Acceleration due to gravity (g) 9.8 ± 0.5 [1.0] 9.8 ± 1.0 [0.5]

Radius of gyration (K) 0.10 ± 0.01 [1.0] 0.10 ± 0.02 [0.5]

Values outside the above mentioned range = Zero

A.Q5(a) Table A.3:

[3.0 marks]

Holes h (m) hˈ (m)

H1 0.243 0.045

H4 0.098 0.11

Each correct value of hˈwithin ± 10 mm [0.5x 2 = 1.0] Values outside the above mentioned range = Zero

(b) Sheet 1: Mark the positions of points of oscillation J1 and J4 on Sheet 1.Label them as J1

and J4 clearly.

[1 x 2 = 2.0]

A.Q6Table A.4: Lengths of equivalent simple pendulums [1.0 mark]

Holes h (m) L (m)

H1 0.243 0.288

H4 0.098 0.209

For each correct calculation within ± 0.015 m [0.5]

10 th

International Junior Science Olympiad,

Pune, India

Experimental Tasks + +

Page 1

Time : 3 hrs

Marks : 40 A B C

Task : In this set of experiments we will investigate, Total Marks: 20

A1: The buffering capacity of milk

A2: Enzymatic digestion of milk proteins

A3: Determining the calcium content of milk

B1 The buffering capacity of milk

B.Q1.A pH of water = [0.25 Mark]

[6.0 – 7.0: 0.25, Other values = Zero]

B.Q1.B pH of sodium carbonate = [0.25 Mark]

[>10: 0.25, Other values = Zero]

B.Q1.C pH of acetic acid = [0.25 Mark]

[2 – 4: 0.25, Other values = Zero]

B.Q1.D pH of milk = [0.25 Mark]

[6.0 – 8.0: 0.25, Other values = Zero]

B

10 th


Pune, India


Page 2

Time : 3 hrs

Marks : 40 A B C

B.Q2 Observation Table B.1 [2.0 Marks]

Marks will be given based on the volume of the solution required to get the desired pH in

each case.

Range of volume: 0.3 - 0.5 ml for each solutions [1 x 2 = 2.0]

0.2 - 0.3 ml or 0.5-0.6 ml for each solutions [0.5 x 2 = 1.0]

Other values = zero.

Stepwise addition to 40 ml water

Sodium carbonate solution Acetic acid solution

Stepwise

volume

added in

ml

pH value Stepwise

volume

added in

ml

pH value

1 0

0

2 0.1

0.1

3 0.1

0.1

4 0.1

0.1

5 0.1

0.1

6 0.1

0.1

7 0.1

0.1

Total …… Volume of Na2CO3 solution

added to reach pH 10.0

…… Volume of CH3COOH solution

added to reach pH 4.0

10 th


Pune, India


Page 3

Time : 3 hrs

Marks : 40 A B C


Stepwise addition to 40 ml Milk

Sodium carbonate solution Acetic acid solution

Stepwise

volume

added in

ml

pH value Stepwise

volume

added in

ml

pH value

1 0

0

2 0.5

0.5

3 0.5

0.5

4 0.5

0.5

5 0.5

0.5

6 0.5

0.5

7 0.5

0.5

Total …… Volume of Na2CO3

solution added to reach

pH 10.0

…… Volume of CH3COOH

solution added to reach pH

4.0

Marks will be given based on the volume of the solution required to get the desired pH in

each case.

Range of volume: 1.5 - 2.5 ml for each solutions [1 x 2 = 2.0]

1.0 - 1.5 ml or 2.5-3.0 ml for each solutions [0.5 x 2 = 1.0]

Other values = zero

10 th


Pune, India


Page 4

Time : 3 hrs

Marks : 40 A B C

Questions:

B.Q4 [1.0 Mark]

Comparing the observations in Table B.1 and B.2 which of the following statements describe

the role played by milk?

a) You require more acetic acid solution to lower the pH of milk to 4 than to lower

the pH of water to 4.

True (T) False (F)

b) Less sodium carbonate solution is required to raise the pH of milk to 10 than to

raise the ph of water to 10

True (T) False (F)

B.Q5 [1.0 Mark] As compared to water, milk resists change in pH of the resulting solution when acetic acid is

added. This is because components of milk:

a) lead to increase in concentration of the OH- ions in the resulting solution

b) prevent increase in concentration of the free H+ ions in the resulting solution

c) lead to decrease in concentration of CH3COO- ions in the resulting solution

Write the correct option in the appropriate box

X

X

b)

10 th


Pune, India


Page 5

Time : 3 hrs

Marks : 40 A B C

B2 Enzymatic digestion of Milk protein

B.Q6.A Iw = [0.5 Mark]

Iw > 0.6 mA [0.5]

Iw = 0.2-0.6 mA [0.25]

B.Q6.B IO = [0.5 Mark]

Anything below 0.2mA or the value based on the curve [0.5]

10 th


Pune, India


Page 6

Time : 3 hrs

Marks : 40 A B C


Time

(in s)

Current

(in mA)

Time

(in s)

Current

(in mA)

1.

16.

2.

17.

3.

18.

4.

19.

5.

20.

6.

21.

7.

22.

8.

23.

9.

24.

10.

25.

11.

26.

12.

27.

13.

28.

14.

29.

15.

30.

20 Readings [0.1 x 20 = 2.0]

10 th


Pune, India


Page 7

Time : 3 hrs

Marks : 40 A B C

B.Q8 Graph plotting: [3.5 Marks]

10 th


Pune, India


Page 8

Time : 3 hrs

Marks : 40 A B C

Plot a graph of current versus time.

Labels on each axis [0.25]

Scale on each axis [0.25]

Marks for occupying more than 60 % of graph paper [0.25]

Drawing smooth curve [0.25]

Based on the plot, within Iw and I0 ranges and the nature of the curve [0.1 x 20 = 2.0]

B.Q9 [1.0 Mark]

Mark a point K on the graph paper where the casein concentration is maximum, a point L where

casein concentration is minimum and a point M where the casein concentration is half-way

between the maximum and minimum values.

Based on the plot, all 3 correct [1.0]

2 correct [0.5]

1 correct [0.25]

B.Q10 [1.0 Mark]

If the increase in current is proportional to the amount of digested casein and maximum current

represents complete digestion of casein, deduce from the graph the time taken for digestion of

50% casein.

Time taken based on the value of M in the above question [1.0]

Other values = Zero

10 th


Pune, India


Page 9

Time : 3 hrs

Marks : 40 A B C

B3 Estimation of calcium content in milk


Sr. No. Titration I Titration II Titration III

1 Initial burette reading

ml

2 Final burette reading ml

3 Difference in burette

reading ml

Average difference in burette reading (m1) = (6.8 – 7.2) [2.0 marks]




Any other Average difference in burette reading: [0.0 marks]

An average value deduced using anomalous reading will result in deduction of 0.25 mark.

B.Q12 [1.0 Mark]

Deduce the amount in milligrams of Ca2+

per 10 ml of the diluted solution (the atomic weight

of Ca is 40).

0.756 mg based on 7.0 ml in the previous question or for correctly calculated value based on the

previous question [1.0]

Wrong calculations [0.5]

Average burette reading: (A)…………………………………ml of 0.001 M Na2EDTA


Pune, India


Page 1

Time : 3 hrs

Marks : 40 A B C

Task : Extraction of lycopene from tomato Total Marks: 6.0

Absorbance of extract:

C.Q1 Observation Table C.1 [3.5 Marks]

Current

in mA

Blue

LED

White

LED

1 Is 0.8 – 1.0

mA

0.6 mA and

above

2 Il 0.0 – 0.08

mA

~ 0.4 mA

Percentage of light

transmitted

0 to 8%

[0.25]

30 – 70%

[0.25]

Is (Blue LED) 0.8 – 1.0 mA [1.5]

Is (Blue LED) 0.6 – 0.8 mA and 1.0 – 1.2 mA [0.75]

Is (White LED) 0.6 mA and above [1.5]

Is (White LED) 0.3-0.6 mA [0.75]

Percentage transmitted in each case [2 x 0.25 = 0.5]

Questions

C.Q2 [1.0 Mark]

If the test tube Ab (containing the solvent) was removed from between the photodiode and the

white LED,

a) The current measured would be less than Is

b) The current measured would be more than Is

c) The current measured would be equal to Is

Write the correct option in the box below.

C

a)


Pune, India


Page 2

Time : 3 hrs

Marks : 40 A B C

C.Q3 [1.5 Marks]

Which of the following can you deduce from your observations in the experiments on transmitted

light. Indicate your answers as YES (Y) or NO (N) in the table below.

a) Lycopene absorbs more blue light relative to other parts of the visible spectrum.

b) Lycopene preferentially absorbs light in the red and yellow parts of the spectrum.

c) Lycopene is an antioxidant.

d) Red and yellow parts of the spectrum are absorbed relatively less compared to

blue parts of the spectrum.

e) Blue light passes through the solution better compared to red light.

f) Lycopene absorbs light equally across the spectrum.

a) Y

b) N

c) N

d) Y

e) N

f) N

Each correct option [0.25]

Time : 3 hrs Marks

: 30

10 th


Multiple Choice Questions

Page 1

1 ) Answer : A Solution : a: 27m3 / 22.4 lt = 10^3 moles = 10^26 molecules

b: 1000/18 = 50 moles = 10^25 atoms

c: 5 seconds for 1 breath => 10^8 breaths

d: 14 billion years => 10^17 seconds

2 ) Answer : A Solution: The sun is just below the horizon. The Moon is just above the

horizon. This implies crescent moon. Since the illumination is from below, answer is A.

3 ) Answer: B Solution :

m =sin i

sin r

sin r =sin i

m=R / 1+ (3 / 4)2R

4

3

=3

5'

cot r =4

3=

R

¢R - R

¢R =7

4R

Area of shadow = 49

16pR2

4 ) Answer B. Solution: The magnetic field above the wire is out of the plane. This flux is

decreasing and

should be compensated by the current in the loop F and so the current in loop F will be

anti- clockwise. For loop G the situation is opposite

5 ) Answer A: Solution : (a) corresponds to p = 0. Then solve for T and put V = 1, a = α, b

= β

6 ) Answer C

7 ) Answer B

8 ) Answer B: Solution : We assume the sign convention where distance measured in the

direction of light propagation are positive, and in opposite direction, negative. For the morning

experiment, since the image of the outside world (object distance u ≈ inf) is real, sharp and

Time : 3 hrs Marks

: 30

10 th



Page 2

inverted, the lens must be converging one, and the image distance (v) is equal to the focal length

(f) of the lens. Thus f = 0.120m. for the evening experiment, the hole in the card serves as the

object of size 0.005m. The image size on the wall is 0.020m.

Distance between the lens and the card u = - uc (uc > 0)

Distance between the lens and the wall v = + vc (vc > 0)

Distance between the lens and wall (question) d = uc + vc

Magnification = v c /−u c = 0.020 / -0.005 = -4 (real images by converging lenses

always have negative magnification, i., inverted image).

Thus, applying the lens formula

1

v−

1

u=

1

f

1

v c+

1

uc=

1

f

1

4uc+

1

uc=

1

f

5

4uc=

1

f

uc =5f / 4 = 5 x 0.120m/4 = 0.150m

vc = 4 uc – 4 x 0.150m = 0.600m

Therefore, the distance between the lens and the wall is

d = uc + vc = (0.15 0 + 0.600)m = 0.750m

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: 30

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Page 3

9 ) Answer D :Solution:

V 1= 300 V t1= 5 min V 2= 200 V t2= 20 min

V 3= 100 V =t3 ? min

Rate of heat supplied by heating container = V

2

R

For first and second container (resistance R is same)

t 1

t 2

=1

4≠

V 1

2

V 2

2=

4

9

Second container should take 2.25 times that of container one but it is taking four times

that of container one. There is some heat loss ( Ploss ) to the environment which is at

lower temperature than ice temperature ( 00

C).

Same amount of heat is being melt in both containers, that means amount of heat supplied

is same.

(V 12

R− P loss)t1=(V 2

2

R− Ploss)t2

which gives Ploss R=5

3×10

4= V loss

2>V 3

2= 10

4

.

Container will loose all heat given by 100 V power supply and ice will cool down instead

of melting.

Additional:

Say outside temp is T 0 and final temperature of ice is T f .

k (0− T 0)= 104×

5

3

k (T f− T0)= 104×1

which gives T f=2

3T 0

Time : 3 hrs Marks

: 30

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10 ) Answer C:

Force at the bottom : Fb

Weight of water : W

Downward vertical force of curved surface on water is : Fg

Then Fb = W + Fg

=> Fg = Fb - W

=> Pb.A -Vg

Fg =ghA – Vg

Fg =g (hA – V)

= 103 x 10 x [ 0.25 x 3.14 x (0.20)

2/4 – 2.5 x 10

-3] N

= 104 x [7.85 -2.50] x 10

-3 N

= 53.5 N

By 3rd law, Fg = vertical force of water on glass

11 ) Answer B : Fig 2 violates Pauli’s exclusion principle and Hund’s rule.

12 ) Answer C: Solution : Grahams law of diffusion

13 ) Answer A : Frendlich isotherms: (lower the temp higher is the adsorption)

14 ) Answer C: Solution : The conductivity that is measured in an electrolyte solution depends

on the type and concentration of the ions. As long as the reaction is taking its course the

conductivity drops, when the standard solution is in surplus the conductivity rises again

15 ) Answer D: Statements (i) and (iii) are correct

16 ) Answer B:

17 ) Answer B: Iron acts as the cathode and oxygen is reduced.

18 ) Answer A: A) I and III are correct

19 ) Answer D: Solution:

[Pb+2

] = 1 x 10-3

cma

aor

m

m

r

r

NH

HCl

NH

HCl 12.815.36

17

20033

Time : 3 hrs Marks

: 30

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[Br-] = 5 x 10

-4

Ionic product = [Pb+2

] [2Br-]

2

Ionic product = [1 x 10-3

] [2x5 x 10-4

]2

10-3+2-8

10-9

As Ksp > ionic product, no precipitate will form.

20 ) Answer D: each of the molecules is planar and triangular.

21 )Answer A: Solution: T is present only in DNA, while U is present only in RNA. If A≠T or

U it is single stranded. If A = T it is most likely to be double stranded. Sample 1 could possibly

be single stranded. However, it is not one of the choices in the correct answer (A).

22 ) Answer B: B) (i), (iv) and (v)

Solution:

If trait is dominant then daughter would show the trait as it would inherit the father’s X-

chromosome. Since son shows the trait, X chromosome inherited from the mother carried

the recessive trait (carrier).

As the daughter would inherit the father’s X-chromosome the daughter is bound to be a

carrier.

As the trait is RARE, marriage outside the family ensures that the mother is likely to not

carry the trait. Hence the son will have ‘0’ probability of inheriting the trait as the X-

chromosome will come from the mother.

23 ) Answer B: (i) and (z); (ii) and (y); (iii) and (x)

Solution: It based on analysis. No prior knowledge is needed.

In case of ‘x’ level of T3 and T4 will be low. As T3 and T4 has a negative effect on TRH

levels, there will be an increase in the levels of TR . Thus ‘x’ matches with ‘iii’

In case of ‘y’ T3 and T4 is low, so TRH levels are high (as explained above). As TRH

positively regulates TSH, TSH levels will increase. Thus ‘y’ matches with ‘ii’

Time : 3 hrs Marks

: 30

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In case of ‘z’ TRH levels are low, thus TSH levels will be low and finally T3 and T4

levels will be low. Thus ‘z’ matches with ‘i’.

24 ) Answer C: C) 1/16

Solution: 14

N: 15

N (start); after 1 cycle two molecules of DNA, 14

N: 15

N and 14

N: 14

N; after 2 cycle

four molecules of DNA, one 14

N: 15

N and three 14

N: 14

N; after 3rd

cycle we will have 8

molecules of DNA, one 14

N: 15

N and rest 7 14

N: 14

N. Finally after the 4th

cycle there will be 16

molecules of DNA of which only one will be hybrid 14

N: 15

N in nature.

25 ) Answer B:

B) Cacti close their stomata during the day, so availability of CO2 for RuBP carboxylase

activity is low during the day.

Solution: To conserve water during the hot days, cacti close stomata during the day. This

reduces the CO2 concentration in the leaf, which cannot support RuBPcase activity.

26 ) Answer D: D) i and iv

Solution: ‘i’ has equal illumination so the seedling does not bend. In ‘iv’ the seedling bends

towards the higher illumination.

27 ) Answer C: C) These organelles have their own genetic material.

Solution: A and C are correct but only C supports the concept of endosymbiosis. B is possible

only for a short duration.

28 ) Answer C: C) T-cells, antibodies and HIV

29 )Answer A: Solution: Population increase under these ideal conditions is called exponential

population growth, giving rise to what is called a J-shaped growth curve. Curve presented in D is

based on logistic model of population growth. B and C are just created as wrong answers.

Comment: Typical growth-curves for populations is a topic mentioned in the syllabus

under Systems – Ecology. See Chapter on Population Ecology in Biology 7th

Edition,

Campbell and Reece for clarification on growth curves.

30 )Answer B: B) Ammonia in tadpole and urea in frog.

Time : 3 hrs Marks

: 30

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Solution: As ammonia has maximum solubility in water, thus tadpole has evolved the

mechanism to generate ammonia as the waste. On the other hand a land animal would generate

urea or uric acid. Frog makes urea.

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