Chapter 1: Introduction to Physics

1.1 Understanding Physics [……/10 x 100 = ………..] explain what physics is recognize the physics in everyday objects and natural phenomena

1. A phenomenon is an (1)occurrence that can be perceived by our (2)senses.2. In physics, we study (3)natural phenomena, such as the eruption of volcano, rain fall, formation

of rainbow and the (4)properties of matter, such as length, temperature, volume3. There are many fields of study in physics, including (5)force, (6)motion, (7)heat, (8)light,

(9)waves, (10)electricity, electromagnetism, electronics and nuclear physics.

1.2 Understanding Base Quantities and Derived Quantities [……/35 x100 =………..] explain what base quantities and derived quantities are list base quantities and their units list some derived quantities and their units. express quantities using prefixes. express quantities using scientific notation express derived quantities as well as their units in terms of base quantities and base units. solve problems involving conversion of units

1. A physical quantity is a (1)physical characteristic that can be (2)measured.2. Base quantities are (3)physical quantities that cannot be defined in terms of other (4)

quantities. There are(5)five base quantities: (6)length, (7)mass, (8)time, (9)current and (10)temperature.

Physical Quantity Base S.I. UnitBase Quantity Quantity Symbol Base S.I. Unit Unit symbol

Length (11) l metre (12) mMass (13)m kilogram (14) kgTime (15)t second (16) s

Electric Current (17)I ampere (18) ATemperature (19)T kelvin (20) K

Table 1.1.1Notes for teachers: Symbol is a short form of a quantity. Example: A boy by the name Ahmad is called as “Mad”; a girl by the

name Mary Jane is called “MJ”; a pet by the name cute-cute is called “cc”.

Unit is similar to the penjodoh bilangan in the Bahasa Melayu. For person, we say “seorang” or “dua orang”; but for a pet like hamsters, we say “seekor” or “dua ekor”.

The unit ampere and kelvin are the names of scientists we use to remind us of their contributions to the respective fields. However, when we write the unit fully, we write all in small letters, example: 1.2 ampere, 5.0 kelvin; when we write shortly, we write the first alphabet of the name in capital letter, example: 1.2 A, 5.0 K

3. Derived quantities are (21)physical quantities consisting of combinations of (22) base quantities., by multiplication, division, or both operations.

4. Derived quantities as well as their units are expressed in terms of base quantities and S.I. units as follows:

1

Notes for teachers:

Example: Given that velocity = . Express the unit for speed in base units.

Solution:

SI unit for velocity =

=

= ms-1 (read as metre per second)

Given that l : length, m : mass, t : time, I : electric current, T : temperature. Derived quantities

(symbol)Expressed in base quantities Derived units

Area(A)

(23) A = l x l (24) Unit A = m x m = (read as square metre)

Volume(V)

(25) V = l x l x l (26) Unit V = m x m x m = (read as cubic metre)

Density( ρ ) (27) Ρ = (28) Unit ρ =

= (read as kilogram per cubic metre)

Speed(v) (29) v = (30) Unit v =

= (read as metre per second)

Work or Energy(W or E)

W = F s F = force s = displacement

Unit W = kg x m = kg = N m = J (read as joule)

Power(P) P = Unit P =

= = W (read as watt)

Velocity(v) v = Unit v =

= (read as metre per second)

Acceleration(a) a =

u = initial velocityv = final velocityt = time taken

Unit a =

= (read as metre per second per second)

Force(F)

F = mam = massa = acceleration

Unit F = kg x = kg = N (read as newton)

2

Impulse(Ft)

Ft = change of momentum = mv – mum = massu = initial velocityv = final velocity

Unit Ft = kg x = kg = N s (read as newton second)

Momentum(p)

p = mvm = mass v = velocity

Unit p = kg x = kg = N s (read as newton second)

Pressure(P) P =

F = forceA = area

Unit P =

= = Pa (read as pascal)

Specific heat capacity

(c)

c =

Q = heat energym = mass

= change in temperature

Unit c =

=

=

= (read as joule per kilogram per kelvin)

Frequency(f) f =

T = period of swing; unit: second (s)

Unit f =

= = Hz (read as hertz)

Electrical charges(Q)

Q = I = electric currentt = time

Unit Q = A s = C (read as coulomb)

Resistance(R) R =

V = voltage; unit: volt (V)I = electric current

Unit R =

= = (read as ohm)

Table 1.1.2

5. Prefixes are used to express some physical quantities that are either very big or very small.

Prefix Symbol ValueTera TGiga GMega M

3

kilo kdeci dcenti cmili mmicronano npico p

Table 1.1.3

6. Standard form or scientific notation: A x 10n where 1 A 10, n is an integer (integer positive or negative).

Ku Physical Quantity Value Standard form or Scientific notation

Mass of earth 6 020 000 000 000 000 000 000 000 kg (31)

Speed or light in the vacuum

299 792 458 m s-1

Radius of earth 6 370 000 m (32)

Mass of hydrogen atom

(33) 0. 000 021 kg

Time of a day 86 400 s

Temperature of the centre of the earth

(34) 6 000 000 K

Size of a flu virus 0.000 000 2 m (35)

Table 1.1.4

1.3 Understanding Scalar and Vector Quantities [……./15x100 = ……..] define scalar and vector quantities give examples of scalar and vector quantities.

1. Scalar quantities are quantities that have (1) magnitude but no (2) direction.2. Vector quantities are quantities that have both (3) magnitude and (4) direction.

Scalar Quantities Vector Quantities

4

Distance (5) DisplacementSpeed (6) VelocityWork (7) AccelerationArea (8) Momentum

Length (9) ImpulseEnergy (10) Force/ weight

Table 1.3.1

*Notes: In the SPM Physics syllabus, there are only six vector quantities, the rest are all scalar quantities. Therefore, the pupils will just have to memorize these six.

3.Distance(s) Displacement(s)

Total length of the path traveled

Distance between two points measured along a specific direction

Scalar quantity Vector quantity

Table 1.3.2Speed Velocity

Rate of change of distance

Rate of change of displacement

Speed = Velocity =

Scalar quantity Vector quantity

Table 1.3.3

Problem Solving:Annie the ant is traveling down the road to buy an umbrella for these rainy days. She walks from her nest, A to B, B to C in 10 minutes’ time as shown in the picture below:(11) What is the distance she traveled? (12) What is her displacement from A?(13) What is her speed? (14) What is her velocity? (15) What is her average speed?

5

Solution:

(11) Distance traveled = AB + BC= 3 m + 4m= 7 m (with unit)

(12) Displacement of the object from A = 5 m towards the direction of AC

tan = 0.75

= 36.9The displacement of the ant is 5 m in the direction of S 36.9 E from A.

(13) Speed = (with unit)

(14) Velocity = (with unit) towards the direction of AC.

(15) Average speed = (with unit)

1.4 Measuring Instruments [………/25 x 100 = …………]

Measure physical quantities using appropriate instruments Explain accuracy and consistency Explain sensitivity Explain types of experimental error Use appropriate techniques to reduce errors

6

A

BC

4 m

3 m

Annie the ant U

Accuracy, Consistency and Sensitivity in Measurement & Errors

Definitions:

1. Consistency in measurements refers to how little (1)deviation there is among the measurements made when a quantity is measured several times.

2. Accuracy of a measurement is how (2) close the measurement made is to the actual value of the quantity.

3. Sensitivity of an instrument is its (3) ability to detect a (4) small change in the quantity to be measured in a short period of time.

4. The diagram shows the result for four shooters A, B, C and D in a tournament. Every shooter shot five times.

The table shows the conclusion:

Table 1.4.1 Figure 1.4.1

5. Error is (9) uncertainty caused by measuring instrument or the observer or the physical factors of the surroundings.

6. Two main types of errors: systematic error and random error.

Systematic Error Random Error Caused by:

i. Error in instrumentsii. Error in calibration

Caused by:i. Surroundings factors, such as

temperature and windii. Carelessness of the observer

Examplei. Zero error

Examplei. Parallax errorii. Error in counting

Cannot be reduced or overcome Can be reduced Way of correction

i. Take the error into account Ways of correction

i. Take several readings and calculate the average value.

Table 1.4.2

Parallax errorsDefinition:A parallax error is an error in reading an instrument because the observer’s eyes and pointer are not (10) in line / perpendicular to the plane of the scale.

Concept & Explanation:

Shooter Consistency AccuracyA High LowB (5) Low HighC High (6) HighD (7) Low (8) Low

7

1. Diagram 1.4.2, Diagram 1.4.3 and Diagram 1.4.4 show the correct positioning of the observer’s eyes to avoid parallax errors.

2. How to avoid parallax error?

(a) position of eyes must be in line/ perpendicular / 90owith the scale of the reading to be taken.

(b) When taking reading from an ammeter, we must make sure that the eyes are exactly in front of the pointer, so that the reflection of the pointer in the mirror is right behind the pointer. In other words, the reflection of the pointer on the mirror could not be seen by the observer, then it is free from parallax error.

Measuring Instruments & Accuracy

Measuring Instruments:

8

Table 1.4.3(A) Instruments measuring length1. Metre Rule

Table 1.4.4

Diagram 1.4.52. Vernier Calipers

The same wire is measured by a vernier caliper. The reading is as follows:

Table 1.4.5

Diagram 1.4.6

3. Micrometer Screw GaugeThe diameter of the wire is measured by a micrometer screw gauge. The reading is as follows:

Diagram 1.4.7 Table 1.4.6

Vernier Calipers

Physical Quantity Measuring InstrumentLength Metre-rule, vernier caliper, micrometer screw gaugeCurrent AmmeterMass Triple-beam-balanceTemperature ThermometerTime Mechanical stopwatch, digital stopwatchVoltage Voltmeter

Ruler A Ruler BSensitivity 0.1 cm 0.5 cmAccuracy 0.1 cm 0.5 cmLength of wire 4.8 cm 5.0 cm

Sensitivity 0.01 cmAccuracy 0.01 cmLength of wire 4.78cm

Sensitivity 0.01 mmAccuracy 0.01 mmDiameter of wire 6.5 +0.22

= 6.72 mm

9

4 5

0 5 10

20

250 5

1) How to read from a vernier calipers?

Figure 8 shows the use of a vernier calipers to measure the size of the inner diameter of a beaker.Inner diameter= main scale reading + vernier scale reading = 3.2 + 0.04= 3.24 cm

wire

2 3 4 510Ruler A

2 3 4 50 1 Ruler B

Positive zero error Negative zero error

Diagram 1.4. 9Positive zero error = + 0.08 cmAll measurements taken with this vernier calipers must be corrected by subtracting 0.08 cm from the readings.

Diagram 1.4.10Negative zero error = - ( 0.1 – 0.08 ) cm = - 0.02 cmAll measurements taken with this vernier calipers must be corrected by subtracting - 0.08 cm, which is adding 0.08 cm to the readings

Eample

(i) Diagram 1.4.11 (ii) Zero error = + 0.04 cmVernier calipers reading = 0.4 + 0.01 = 0.41 cmCorrected reading = vernier calipers reading – zero error= 0.41 – 0.04= 0.37 cm

Example

(i) Diagram 1.4.12 (ii) Zero error = -(0.1 – 0.07) cm = - 0.03 cmVernier calipers reading = 3.6 + 0.02 = 3.62 cmCorrected reading = vernier calipers reading – zero error= 3.62 – (-0.03)= 3.62 + 0.03= 3.65 cm

10

Write down the readings shown by the following diagrams:

No. Diagram Answer

11 4.89 cm

12 8.77 cm

13 2.28 cm

14 0.52 cm

15 The following diagram shows the scale of a pair of vernier callipers when the jaws are closed. State the zero error.

+ 0.02 cm

16 The following diagram shows the scale of the same vernier callipers as in Question No. (15) above when there are 40 pieces of cardboard between the jaws. Calculate the thickness of a piece of cardboard.

6.14 – (+ 0.02)

= 6.12 cm

Thus, thickness of a piece of paper

=

11

0 5 10

0 1

Micrometer Screw Gauge

1) How to read from a micrometer screw gauge?

Diagram 1.4.13Figure 13 shows the use of a micrometer screw gauge to measure the size of a spherical object.Main scale reading = 5.5 mmThimble scale reading = 12 x 0.01

= 0.12 mmFinal reading = 5.5 + 0.12

= 5.62 mm

2. Positive zero error and negative zero error

Positive zero error Negative zero error

12

Diagram 1.4.14 Positive zero error = + 0.04 mmAll measurements taken with this micrometer screw gauge must be corrected by subtracting 0.04 mm from the readings

Diagram 1.4.15

Negative zero error = - 0.04 mmAll measurements taken with this micrometer screw gauge must be corrected by subtracting - 0.04 mm, which is adding 0.04 mm from the readings

Example

Diagram 1.4.16 Zero error = + 0.01 mmmicrometer screw gauge reading= 2.5 + 0.35= 2.85 mmCorrected reading = micrometer screw gauge reading – zero error= 2.85 – 0.01= 2.84 mm

Example

Diagram 1.4.17Zero error = - 0.03 mmmicrometer screw gauge reading = 6.0 + 0.08= 6.08 mmCorrected reading = micrometer screw gauge reading – zero error= 6.08 – (-0.03)= 6.08 + 0.03= 6.11 mm

Write down the readings shown by the following micrometer screw gauges.

(17) (18)

13

25

300 5

40

5 10 15 45

Answer: 6.5 + 0.28 = 6.78 mm Answer: 17.0 + 0.42 = 17.42 mm

(19) (20)

Answer: 4.5 + 0.06 = 4.56 mm Answer: 9.0 + 0.32 = 9.32 mm

Determine the readings of the following micrometer screw gauges.

(21) Zero error = - 0.02 mm (22) Zero error = + 0.02 mm

Determine the readings of the following micrometer screw gauges.

(B) Instrument Measuring Current : Ammeter:

Ammeter ranged 0.0 A – 5.0 ASensitivity = 0.1 AAccuracy = 0.1 A

14

0 0

45

5

0

0

5

0

0 0 5

15

20

30

350 5

(23) Zero error = + 0.03 mm (24) Reading shown = 6.5 + 0.18 = 6.68 mm

(25) Corrected reading = 6.68 – (+0.03) = 6.65 mm

5

100

Diagram 1.4.18

Doubled ranged ammeter:

Upper scale ranged 0.0 A – 5.0A; Sensitivity = 0.1 A ; accuracy = 0.1 ALower scale ranged 0.00A – 1.00A; Sensitivity = 0.02A ; accuracy = 0.02AReading = 0.30 A

Diagram 1.4.19

Miliammeter (0 mA – 50 mA):

Sensitivity = 1 mA

Accuracy = 1 mA

Reading = 15 mA

Diagram 1.4.20

(C) Instrument Measuring Temperature Thermometer

15

Diagram 1.4.21Accuracy = 1

oC

(D) Instrument Measuring Time

Mechanical Stopwatch Accuracy = 0.2 s; Reading = 8.2 s

1.5 Scientific Investigation [……/12 x 100 = …………] Identify variables in a given situation Identify a queation suitable for scientific investigation

16

Digital StopwatchAccuracy = 0.01sReading = 3 minutes 55.62 s

Diagram 1.4.22: Mechanical stopwatch

Diagram 1.4.23: Digital stopwatch

Form a hypothesis Design and carry out a simple experiment to test the hypothesis Record and present data in a suitable form Interpret data to draw a conclusion Write a report of the investigation

Clone of SPM Trial Exam of the Perak State year 2003: Paper 3 / Section B/ Question 2

Notes: MV -manipulated variable; RV-responding variable; C- constant

Two twin brothers, Micheal and Jackson, of the same size, are swinging happily on the swings at a playground as shown in the figure above.However, the ropes that is holding the swing where Micheal is sitting is longer than Jackson’s. And, Micheal notices that his swing is swinging slower than his brother, Jackson. Using this information;(a) make a suitable inference, [1 mark](b) state one appropriate hypothesis that could be investigated, [1 mark](c) describe how you would design an experiment to test your hypothesis using a bob, strings and other

apparatus.In your description, state clearly the following:(i) aim of the experiment(ii) variables in the experiment(iii) list of apparatus and materials(iv) arrangement of the apparatus(v) the procedure of the experiment, which includes the method of controlling the manipulated

variable and the method of measuring the responding variable.(vi) the way you would tabulate the data(vii) the way you would analyze the data [10 marks]

Answer: (a) (1) Length of ropes influences time of making a complete swing(b) (2) When the length of pendulum increases, the period of swing increases.

17

Keywords to indicate C is mass

Keywords to indicate MV is length

Keywords to indicate RV is time of making a complete swing

Keywords to indicate the must-use-apparatus and hinting on the Pendulum experiment

(c)

Marks

1st mark Aim: To investigate the relationship between length of pendulum and period of swing.

2nd mark Manipulated Variable (MV): length of pendulum, l

Responding Variable (RV): period of swing, T

3rd mark Constant: mass of bob

4th mark

List of apparatus & materials:Measuring instruments: Metre rule & stopwatch , Others: bob, string, retort stand and clamp, split cork,

(The measuring instruments carry marks. If all apparatus are listed except metre-rule and stopwatch, pupils will lose the 4th mark.)

5th mark

Arrangement of apparatus:

6th mark Method to control MV *Measure l = 10.0 cm by using a metre rule.

Vital Notes & Information for Teachers & Pupils :

18

Active or passive sentences are acceptable. Most importantly, the pupils must state a value and measuring instrument for

the 6 th mark. The steps stated as * are the most essential steps (though they are very short) to

entitled pupils for 6th & 7th marks in the exam. Teachers/ pupils could add in some other steps to make the procedure clearer for

PEKA Physics . However, the sentence “ The apparatus as shown in the diagram above is set

up.” will cause the pupils to lose all the marks from the 6th onwards if the diagram drawn is incorrect / unfunctional. Therefore, the pupils should avoid writing this sentence since it is understood and does not carry any marks but could be very ‘disastrous’.

7th mark

Method to control RV

*Measure time for 20 swings, t20 by using a stopwatch.

Calculate period of a swing, T as follows:

Vital Notes & Information for Teachers & Pupils : Active or passive sentences are acceptable. Most importantly, the pupils must state measuring instrument(s) for the 7 th mark.

8th mark Repetition:Repeat the experiment with l = 20.0 cm, 30.0 cm, 40.0 cm, 50.0 cm using the same bob.

9th mark : Tabulate data l (cm) T (s)10.020.030.040.050.0

10th mark : Analyze data Plot graph T(s) against l (cm)

19

T (s)

l (cm)