PREFACE - · PDF fileQuick Exam Notes N(A) Level Science (Physics) ... 10.4 Evaporation. Quick Exam Notes NA SciPhysics.i4 4 9/21/2015 3:32:54 PM. Section iV: waVeS cHaPter 11:

PREFACE

Quick Exam Notes N(A) Level Science (Physics) is specially compiled to help students prepare for important tests and examinations.

Clear Presentation FormatNotes are presented in point form for ease of understanding and systematic learning. Students will be able to review important concepts and examples quickly.

Useful IllustrationsA variety of diagrams, graphs and tables are included. Students will be able to understand concepts and processes easily through these helpful visual aids.

The Editorial Team

Quick Exam Notes NA SciPhysics.i1 1 9/21/2015 3:32:54 PM

CONTENTS

Section i: MeaSureMent

cHaPter 1: Physical Quantities, units and Measurement 1

1.1 International System of Units (SI Units)1.2 Scalar and Vector1.3 Measuring Length1.4 Measuring Time

Section ii: newtonian MecHanicS

cHaPter 2: Kinematics 10

2.1 Speed and Velocity2.2 Displacement-Time Graph2.3 Velocity-Time Graph2.4 Acceleration Due to Gravity


cHaPter 3: Dynamics 143.1 DefinitionofForce3.2 Resultant Force3.3 Newton’s Laws of Motion3.4 Friction3.5 Balanced Forces3.6 Unbalanced Forces

cHaPter 4: Mass, weight and Density 184.1 Mass4.2 Weight4.3 Density

cHaPter 5: turning effect of Forces 215.1 Moment of a Force5.2 Principle of Moments5.3 Centre of Gravity (CG) of Regularly-shaped Objects5.4 Stability

cHaPter 6: Pressure 256.1 Pressure6.2 Mercury Barometer


cHaPter 7: work, energy and Power 277.1 Work7.2 Energy7.3 Power

Section iii: tHerMal PHySicS

cHaPter 8: Kinetic Model of Matter 308.1 States of Matter8.2 Kinetic Theory of Matter8.3 Brownian Motion

cHaPter 9: transfer of thermal energy 329.1 Methods of Heat Transfer9.2 Conduction9.3 Convection9.4 Radiation9.5 Application of Heat Transfer – A Vacuum Flask9.6 Experiments to Investigate Absorption and Emission of Radiation by Black and Silvery Surfaces

cHaPter 10: thermal Properties of Matter 3710.1 Internal Energy10.2 MeltingandSolidification10.3 Boiling and Condensation10.4 Evaporation


Section iV: waVeS

cHaPter 11: General wave Properties 42

11.1 Waves11.2 Wave Properties11.3 Mechanical Wave Generator11.4 ReflectionandRefractionofWaves

cHaPter 12: electromagnetic Spectrum 47

12.1 Electromagnetic Spectrum12.2 Common Properties of All Electromagnetic Waves12.3 Examples of Uses of Electromagnetic Waves

cHaPter 13: Sound 4913.1 Nature of Sound13.2 Transmission Medium for Sound13.3 Audible Range13.4 ReflectionofSoundWaves–Echoes13.5 Pitch13.6 Loudness


Section V: electricity

cHaPter 14: current of electricity 5514.1 Conventional Current14.2 Electric Current14.3 Electromotive Force (e.m.f.)14.4 Potential Difference (p.d.)14.5 Resistance

cHaPter 15: D.c. circuits 61

15.1 Circuit Symbols15.2 Potential Divider15.3 Thermistor15.4 Light-dependent Resistor

cHaPter 16: Practical electricity 63

16.1 Practical Usage of Electricity16.2 Electrical Power16.3 Electric Energy16.4 Calculating Electrical Consumption16.5 Electrical Plug Wiring16.6 Safe Use of Electricity16.7 Dangers of Electricity

aPPenDiX: PHySicS ForMula liSt 69


� © Singapore Asia Publishers Pte Ltd

CHAPTER 1 PhySiCAl QuANTiTiES, uNiTS ANd MEASuREMENT

�.� International System of Units (SI Units)• All other physical quantities are derived from the seven basic physical quantities, namely mass, length,

time, electric current and temperature.* • The other two basic physical quantities are amount of substance (mole) and luminous intensity

(candela). • The SI units are listed in the table below.

Basic physical quantity Si unit Si unit symbol

Mass kilogram kg

Length metre m

Time second s

Electric current ampere A

Temperature kelvin K

* Out of the seven quantities, only these five are covered in the N(A) Level Science (Physics) Syllabus.



Chapter 1 Physical Quantities, Units and Measurement

Prefixes for SI Units• Inpractice,weoftenexpressthesenumbersbystandardformoruseaprefixtorepresentthesenumbers.

Standard form Prefix Symbol

106 mega M

103 kilo k

10−2 centi c

10−3 milli m

10−6 micro µ

�.� Scalar and Vector• A scalar quantity has only magnitude but no direction.• A vector quantity has both magnitude and direction.

Scenario to Differentiate Scalar and Vector Quantities

Town BTown A

Town C

40 km

30 km

N




• A man cycles from Town A to Town B in 4 hours. • He continues to cycle from Town B to Town C in 3 hours. • Total time taken to travel from Town A to Town C is 7 hours.

Scalar Vector

• total distance travelled = 70 km• The direction of travel is not important.

• Displacement (A to C) = 50 km• Cyclist travelled from Town A to Town C, a bearing of 126.9°.

• Average speed = Total distance _____________ Total time taken = 70 ___ 7 = 10 km h–1 • Average velocity = Displacement

_____________ Total time taken = 50 ___ 7 = 7 1 __ 7 km h−1

• acceleration is the rate of change of velocity.

• a = ∆v ___ ∆t = v – u _____ t

• SI unit is m s−2.

�.� Measuring Length• Common instruments for measuring length include measuring tape, metre rule or half-metre rule,

vernier calipers and micrometer screw gauge.

length (l) to be measured instrument accuracy

l > 1 m measuring tape ± 0.1 cm

10 cm < l < 1 m metre rule / half-metre rule ± 0.1 cm

1 cm < l < 10 cm vernier calipers ± 0.01 cm

l < 2 cm micrometer screw gauge ± 0.001 cm




Parallax Error• This occurs due to wrong techniques of reading off measurement from measuring instruments. • To avoid committing such an error, always read off directly vertically above the mark on the measuring

instrument.

Vernier Calipers• This instrument consists of a main scale and a vernier scale.• The table below shows the procedures to read off measurements using the vernier calipers.

Diagrams Procedures

1. Check for zero error. Close the calipers fully without any object.

(i) If the zero mark on the vernier scale coincides with the zero mark on the main scale, there is no zero error.

(ii) If the zero mark on the vernier scale is to the right of the main scale, this is a positive zero error, hence it has a positive value. (In this example, the zero error is 0.12 cm.)

(iii) If the zero mark on the vernier scale is to the left of the main scale, this is a negative zero error, hence it has a negative value. (In this example, the zero error is –0.02 cm. [Count backwards from 10.])

(iv) Record this number as the zero error C.

0 cm 1main scale

0 10vernier scale

0 cm 1

0 102

0 cm 1

0 108




2. Place the object between the calipers and close the calipers fully. (Be careful not to over-tighten.)

(i)

(ii)

0 2 3 4 5 6

2 3

0 10

(i) Read off the main scale directly on top of the zero mark of the vernier scale. Record this number A.

In this case, A = 2.4 cm.

(ii) Look out for the place where the marking on the main scale coincides with the marking on the vernier scale. Record this number B (B = 0.0x cm where x is any number from 0 to 9).

In this case, B = 0.08 cm.

3. The reading is given by: A + B – C (in centimetres).

zero error




Micrometer Screw Gauge• This instrument consists of a main scale (1 mm per division), sleeve (0.5 mm per division) and thimble

scale (0.01 mm per division).• The table below shows the procedures to read off measurements using the micrometer screw gauge.

Diagrams Procedures

1. Check for zero error. Close the gauge fully by turning the ratchet until a clicking sound is heard.

(i) If the datum line coincides with the zero mark on the thimble scale, there is no zero error.

(ii) If the datum line is above the zero mark on the thimble scale, the zero error is positive. (In this example, the zero error is 0.03 mm.)

(iii) If the datum line is below the zero mark on the thimble scale, the zero error is negative. (In this example, the zero error is –0.03 mm. Note: Count backwards from 0.)

0datumthimble

5

0

0

45




2. Place the object in the gauge and tighten fully. (Be careful not to over-tighten.) Read the main scale (pay attention to the sleeve reading) at the edge of the thimble.

(i) The main scale reading in this case is 2.0 mm and the thimble reading is 37, which means 0.37 mm. As such, the reading is 2.0 + 0.37 = 2.37 mm.

(ii) The main scale reading in this case is 1.5 mm and the thimble reading is 38, which means 0.38 mm. As such, the reading is 1.5 + 0.38 = 1.88 mm.

�.� Measuring Time• To measure long intervals of time (in hours, minutes and seconds), we use watches and pendulum

clock.• To measure short intervals of time, we use a digital stopwatch (accuracy up to ± 0.01 s) or a ticker-tape

timer (smallest time division is 0.02 s).

Ticker-tape Timer• A ticker-tape timer is a machine that makes a dot on paper (or a piece of ticker-tape — long strip of

paper)atfixedintervalsoftime.Thisisusually50dotspersecond,whichmeansthatthetimebetweentwo consecutive dots is 0.02 s.

40

35

0main

sleeve

1 2

0.5 1.5

40

35

0

sleeve

1

0.5 1.5




• When the ticker-tape timer is attached to a moving object, it can be used to measure the speed of an object.

• The speed of the ticker-tape can be calculated by measuring the length of the tape (L) and counting the number of intervals (N) between the dots.

Speed = Distance ________ Time = L ________ 0.02 × N

Period of Oscillation• Oscillations are repeated, periodic motions of an object.

AmplitudeB C

D

• When the bob of a simple pendulum completes the move: C−D−C−B−C, the bob is said to have completed one oscillation.

• Period is the time taken to complete one oscillation.• For a simple pendulum experiment, we would usually take the time for 20 oscillations of the pendulum

and repeat the timing to get two readings, t1 and t2.


�� © Singapore Asia Publishers Pte Ltd

CHAPTER 3

dyNAMiCS

�.� Definition of Force• A force is a push or pull that is exerted by one object on another. It can cause an object to start moving

or stop moving. The SI unit of force is newton (N).

Examples of Forces• Weight−thepullofgravitationalforceonanobject• Friction−contactforcebetweentwosurfacesthatcausesobjectstoslowdown• Magnetic force−theforceexperiencedbyanobjectwhenplacedinamagneticfield• Electric force−theforceexperiencedbyanobjectwhenplacedinanelectricfield

�.� Resultant Force• The resultant force is the combination of two or more forces, taking into account the magnitudes and

directions of the original forces.• For forces that point in the same direction, we can either add or subtract to obtain the resultant force.

Resultant force, FR = 20 + 15 – 10 = 25 N to the right.

F1 = 20NF3 = 10N

F2 = 15N


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PREFACE - · PDF fileQuick Exam Notes N(A) Level Science (Physics) ... 10.4 Evaporation. Quick Exam Notes NA SciPhysics.i4 4 9/21/2015 3:32:54 PM. Section iV: waVeS cHaPter 11: