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Combined and Co-ordinated Sciences
The workbook:
• Focuses on the skills students need for scientific study, including
problem-solving, handling, interpreting and presenting data, as well as
investigating and experimenting.
• Contains exercises that are arranged in the same order as the chapters
in the Physics section of the coursebook, and are clearly marked
according to the syllabus they cover.
• Is written in a clear and accessible style with the international learner
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Cambridge IGCSE®
Cambridge IGCSE® Combined and
Co-ordinated Sciences
Physics Workbook
David Sang
David Sang
Cambridge IGCSE®
Combined and
Co-ordinated
Sciences
Physics Workbook
Physics Workbook
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about the syllabuses
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David Sang
Cambridge IGCSE®
Combined and
Co-ordinated
Sciences
Physics Workbook
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Original material © Cambridge University Press 2017
Contents
Introductionv
P7 Energy resources
38
P7.01 Renewables and non-renewables
38
P7.02 Wind energy
39
P7.03 Energy from the Sun
41
P1 Making measurements
1
P1.01 The SI system of units
1
P1.02 Accurate measurements
2
P1.03 Density data
3
P8 Work and power
42
P1.04 Testing your body clock
5
P8.01 Forces doing work, transferring energy
42
P2 Describing motion
7
P8.02 Calculating work done
43
P2.01 Measuring speed
7
P8.03 Measuring work done
45
P2.02 Speed calculations
9
P8.04 Power
46
P2.03 More speed calculations 10
P9 The kinetic model of matter
48
P2.04 Distance–time graphs 11
P9.01 Changes of state
48
P2.05 Acceleration 14
P9.02 The kinetic model of matter
49
P2.06 Speed–time graphs 15
P9.03 Brownian motion
50
P3 Forces and motion
17
P9.04 Understanding gases
51
P3.01 Identifying forces
17
P10 Thermal properties of matter
52
P3.02 The effects of forces
18
P10.01 Demonstrating thermal expansion
52
P3.03 Combining forces
19
P10.02 Thermal expansion
53
P3.04 Mass and weight
20
P10.03 Energy and temperature
55
P3.05 Force, mass and acceleration
20
P10.04 Calibrating a thermometer
55
P4 Turning effects of forces
22
P4.01 Turning effect of a force
22
P11 Thermal (heat) energy
transfers57
P4.02 Calculating moments
23
P4.03 Stability and centre of mass
24
P4.04 Make a mobile
25
P5 Forces and matter
26
P5.01 Stretching a spring
26
P5.02 Stretching rubber
28
P5.03 Pressure
P11.01 Conductors of heat
57
P11.02 Convection currents
59
P11.03 Radiation
60
P11.04 Losing heat
62
P11.05 Warming up, cooling down
63
P12 Sound
65
29
P12.01 Sound on the move
65
P6 Energy transformations and
energy transfers
P12.02 Sound as a wave
68
31
P13 Light
70
P6.01 Recognising forms of energy
31
P13.01 On reflection
71
P6.02 Energy efficiency
33
P13.02 Refraction of light
72
P6.03 Energy calculations
P13.03 The changing speed of light
35
Original material © Cambridge University Press 2017
73
iii
Cambridge IGCSE Combined and Co-ordinated Sciences
iv
P13.04 A perfect mirror
74
P19 Electric circuits
99
P13.05 Image in a lens
75
P19.01 Circuit components and their symbols
99
P14 Properties of waves
77
P19.02 Resistor combinations
100
P14.01 Describing waves
77
P19.03 More resistor combinations
102
P14.02 The speed of waves
79
P19.04 Electrical safety
104
P14.03 Wave phenomena
80
P20 Electromagnetic forces
106
P15 Spectra
82
P20.01 Using electromagnetism
106
P15.01 Electromagnetic waves
82
P21 Electromagnetic induction
108
P15.02 Using electromagnetic radiation
83
P21.01 Electricity generation
108
P16 Magnetism
85
P21.02 Transformers
109
P16.01 Attraction and repulsion
85
P22 The nuclear atom
112
P16.02 Magnetic fields
86
P22.01 The structure of the atom
113
P17 Electric charge
87
P22.02 Isotopes
114
P17.01 Attraction and repulsion
87
P22.03 The nature of radiation
115
P17.02 Static at home
89
P22.04 Radioactive decay equations
116
P18 Electrical quantities
90
P22.05 Radioactive decay
118
P22.06 Using radioactive substances
121
P18.01 Current in a circuit
91
P18.02 Current and charge
92
P18.03 Electrical resistance
93
P18.04 Current–voltage characteristics
95
P18.05 Electrical energy and power
97
Answers122
Original material © Cambridge University Press 2017
Introduction
This workbook covers two syllabuses: Cambridge IGCSE Combined Science (0653) and
Cambridge IGCSE Co-ordinated Sciences (0654). Before you start using this workbook, check with
your teacher which syllabus you are studying and which papers you will take. You will sit either the
Core paper or the Extended paper for your syllabus. If you are sitting the Extended paper, you will
study the Core material and the Supplement material for your syllabus.
Once you know which paper you will be sitting, you can use the exercises in this workbook to help
develop the skills you need and prepare for your examination.
The examination tests three different Assessment Objectives, or AOs for short. These are:
AO1 Knowledge with understanding
AO2 Handling information and problem solving
AO3 Experimental skills and investigations.
In the examination, about 50% of the marks are for AO1, 30% for AO2 and 20% for AO3. Just learning
your work and remembering it is therefore not enough to make sure that you get the best possible grade
in the exam. Half of all the marks are for AO2 and AO3. You need to be able to use what you’ve learned in
unfamiliar contexts (AO2) and to demonstrate your experimental skills (AO3).
There are lots of activities in your coursebook which will help you to develop your experimental skills by
doing practical work. This workbook contains exercises to help you to develop AO2 and AO3 further.
There are some questions that just involve remembering things you have been taught (AO1), but most of
the questions require you to use what you’ve learned to work out, for example, what a set of data means,
or to suggest how an experiment might be improved.
v
These exercises are not intended to be exactly like the questions you will get on your exam papers.
This is because they are meant to help you to develop your skills, rather than testing you on them.
There’s an introduction at the start of each exercise that tells you the purpose of it – which skills you
will be working with as you answer the questions.
There are sidebars in the margins of the book to show which material relates to each syllabus and paper.
If there is no sidebar, it means that everyone will study this material.
Original material © Cambridge University Press 2017
v
Cambridge IGCSE Combined and Co-ordinated Sciences
Use this table to ensure that you study the right material for your syllabus and paper:
Cambridge IGCSE Combined Science (0653)
Cambridge IGCSE Co-ordinated Sciences (0654)
Core
Supplement
Core
Supplement
You will study the
material:
You will study the
material:
You will study the
material:
Without a
sidebar
Without a
sidebar
Without a
sidebar
You will study
everything.
This includes the
material:
With a double
grey sidebar
With a single
grey sidebar
With a double
black sidebar
With a double
grey sidebar
Without a
sidebar
With a single
grey sidebar
With a double
grey sidebar
With a single
black sidebar
With a double
black sidebar
Safety
vi
A few practical exercises have been included. These could be carried out at home using simple materials that
you are likely to have available to you. (There are many more practical activities on the CD-ROM that accompanies
your coursebook.)
While carrying out such experiments, it is your responsibility to think about your own safety, and the safety of
others. If you work sensibly and assess any risks before starting, you should come to no harm. If you are in doubt,
discuss what you are going to do with your teacher before you start.
Original material © Cambridge University Press 2017
Chapter P1
Making measurements
KEY TERMS
density: the ratio of mass to volume for a substance
USEFUL EQUATIONS
density =
mass
volume
Exercise P1.01 The SI system of units
To be part of the international community of scientists, you need to use the SI units
(Le Système International d’Unités).
a Give the SI units (name and symbol) of the following quantities:
length
1
volume
b Give the name in words and the symbol for the following:
one thousand metres
one-thousandth of a metre
c How many
centimetres are there in a metre?
litres are there in a cubic metre?
d List as many non-SI units of length as you can.
Original material © Cambridge University Press 2017
1
Cambridge IGCSE Combined and Co-ordinated Sciences
e Give a reason why it is important for scientists to have a system of units that is agreed between all countries.
f
Name some more professions that make use of the SI system of units.
Exercise P1.02 Accurate measurements
To measure a length accurately, it is essential to have a careful technique. This exercise will test
your ability to measure lengths.
a The diagram shows how a student attempted to measure the length of a piece of wire.
0
2
1
2
3
4
5
6
7
From the diagram, estimate the length of the wire. State three ways in which the student could have improved his technique for measuring the wire.
b Find a rectangular sheet of paper, at least as big as the pages of this book. A sheet of newspaper is ideal.
Your task is to use a ruler to measure three lengths: the short side, the long side and the diagonal.
For lengths that are longer than your ruler, you will need to devise a careful technique.
c Describe the method you have used for measuring the length of the diagonal. It may help to include a diagram.
Original material © Cambridge University Press 2017
Chapter P1: Making measurements
d Record your results (in centimetres) in Table 1.01.
Measurement
Length / cm
Length2 / cm2
short side
long side
diagonal
Table 1.01
e Now you can use Pythagoras’ theorem to test your results. In the third column of the table, calculate and
write down the square of each length.
Then calculate:
(short side)2 + (long side)2 = This should be equal to (diagonal)2.
f
Round off your values to the nearest cm2. How close are your two answers? Write a comment below.
Exercise P1.03 Density data
3
This exercise presents some data for you to interpret and use.
Some data about the density of various solids and liquids are shown in Table 1.02.
Material
water
ethanol
olive oil
mercury
ice
diamond
cork
chalk
iron
tungsten
aluminium
gold
State / type
liquid / non-metal
liquid / non-metal
liquid / non-metal
liquid / metal
solid / non-metal
solid / non-metal
solid / non-metal
solid / non-metal
solid / metal
solid / metal
solid / metal
solid / metal
Density / kg/m3
1000
800
920
13 500
920
3500
250
2700
7900
19 300
2700
19 300
Density / g/cm3
1.000
0.800
Table 1.02
Two units are used for the densities, kg/m3 and g/cm3.
a Complete the fourth column by converting each density in kg/m3 to the equivalent value in g/cm3.
The first two have been done for you.
Original material © Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
b Ice floats on water because its density is less than that of water. Name another solid material shown in the
table which will float in water.
c A cook mixes equal volumes of water and olive oil in a jar. The two liquids separate. Complete the drawing of
the jar to show how the liquids will appear. Label them.
4
d A student wrote: “These data show that metals are denser than non-metals.” Do you agree?
Explain your answer.
e Calculate the mass of a block of gold that measures 20 cm × 15 cm × 10 cm. Give your answer in kg.
Original material © Cambridge University Press 2017
Chapter P1: Making measurements
f
A metalworker finds a block of silvery metal. He weighs it and he measures its volume. Here are his results:
mass of block = 0.270 kg
volume of block = 14.0 cm3
Calculate the density of the block.
Suggest what metal this might be. Exercise P1.04 Testing your body clock
How good would your pulse be as a means of measuring time intervals?
Galileo used the regular pulse of his heart as a means of measuring intervals of time until he noticed that a
swinging pendulum was more reliable.
In this exercise, you need to be able to measure the pulse in your wrist. Place two fingers of one hand gently on the
inside of the opposite wrist. Press gently at different points until you find the pulse. (Alternatively, press two fingers
gently under your jawbone on either side of your neck.)
You will also need a clock or watch that will allow you to measure intervals of time in seconds.
a Start by timing 10 pulses. (Remember to start counting from zero: 0, 1, 2, 3, …, 9, 10.) Repeat this several times
and record your results in a table in the space provided.
b Comment on your results. How much do they vary? Is the problem that it is difficult to time them, or is your
heart rate varying?
Original material © Cambridge University Press 2017
5
Cambridge IGCSE Combined and Co-ordinated Sciences
c Use your results to calculate the average time for one pulse.
d Repeat the above, but now count 50 pulses. Record your results in a table in the space provided.
Calculate the average time for one pulse.
6
e Now investigate how your pulse changes if you take some gentle exercise – for example, by walking briskly, or
by walking up and down stairs.
Write up your investigation in the lined space. Use the following as a guide.
•
Briefly describe your gentle exercise.
•
Give the measurements of pulse rate that you have made.
•
Comment on whether you agree with Galileo that a pendulum is a better time-measuring instrument than
your pulse.
Original material © Cambridge University Press 2017
Chapter P2
Describing motion
KEY TERMS
speed: the distance travelled by an object in unit time
acceleration: the rate of change of an object’s velocity
USEFUL EQUATIONS
speed =
distance
acceleration =
time
speed = gradient of distance–time graph
change in speed
time taken
acceleration = gradient of speed–time graph
distance = area under speed–time graph
Exercise P2.01 Measuring speed
This exercise is about how we can measure the speed of a moving object.
a One way to find the speed of an object is to measure the time it takes to travel a measured distance.
Table 2.01 shows the three quantities involved.
7
Complete the table as follows:
•
In the second column, give the SI unit for each quantity (name and symbol).
•
In the third column, give some other, non-SI, units for these quantities.
•
In the fourth column, name suitable measuring instruments for distance and time.
Quantity
SI unit (name and symbol)
Non-SI units
Measuring instrument
distance
time
speed
Table 2.01
b In the laboratory, the speed of a moving trolley can be found using two light gates. A timer measures the time
taken for a trolley to travel from one light gate to the other.
What other quantity must be measured to determine the trolley’s speed?
Write down the equation used to calculate the speed of the trolley
Original material © Cambridge University Press 2017
7
Cambridge IGCSE Combined and Co-ordinated Sciences
A trolley takes 0.80 s to travel between two light gates, which are separated by 2.24 m.
Calculate its average speed.
c The speed of moving vehicles is sometimes measured using detectors buried in the road. The two detectors
are about 1 m apart. As a vehicle passes over the first detector, an electronic timer starts. As it passes over the
second detector, the timer stops.
Explain how the vehicle’s speed can then be calculated.
8
On one stretch of road, any vehicle travelling faster than 25 m/s is breaking the speed limit. The detectors are
placed 1.2 m apart. Calculate the speed of a car that takes 0.050 s to travel this distance. Is it breaking the
speed limit?
Calculate the shortest time that a car can take to cross the detectors if it is not to break the speed limit.
Original material © Cambridge University Press 2017
Chapter P2: Describing motion
d Describe briefly how such a speed-detection system could be used to light up a warning light whenever a
speeding car goes past.
Exercise P2.02 Speed calculations
Use the equation for speed to solve some numerical problems.
a The table shows the time taken for each of three cars to travel 100 m. Circle the name of the fastest car.
Complete Table 2.02 by calculating the speed of each car. Give your answers in m/s and to one decimal place.
Car
Time taken / s
red car
4.2
green car
3.8
yellow car
4.7
Speed / m/s
Table 2.02
b A jet aircraft travels 1200 km in 1 h 20 min.
How many metres does it travel? For how many minutes does it travel? And for how many seconds? Calculate its average speed during its flight.
c A stone falls 20 m in 2.0 s. Calculate its average speed as it falls.
Original material © Cambridge University Press 2017
9
Cambridge IGCSE Combined and Co-ordinated Sciences
The stone falls a further 25 m in the next 1.0 s of its fall. Calculate the stone’s average speed during the
3 s of its fall.
Explain why we can only calculate the stone’s average speed during its fall.
Exercise P2.03 More speed calculations
In these problems, you will have to rearrange the equation for speed.
10
a A car is moving at 22 m/s. How far will it travel in 35 s?
b A swallow can fly at 25 m/s. How long will it take to fly 1.0 km?
c A high-speed train is 180 m long and is travelling at 50 m/s. How long will it take to pass a person standing at a
level crossing?
Original material © Cambridge University Press 2017
Chapter P2: Describing motion
How long will it take to pass completely through a station whose platforms are 220 m in length?
d In a 100 m race, the winner crosses the finishing line in 10.00 s. The runner-up takes 10.20 s. Estimate the
distance between the winner and the runner-up as the winner crosses the line. Show your method of working.
Explain why your answer can only be an estimate.
11
Exercise P2.04 Distance–time graphs
In this exercise, you draw and interpret some distance–time graphs. You can calculate the speed
of an object from the gradient (slope) of the graph.
a The diagrams A–D show distance–time graphs for four moving objects. Complete Table 2.03 by indicating
(in the second column) the graph or graphs that represent the motion described in the first column.
Time
Description of motion
Time
Distance
D
Distance
C
Distance
B
Distance
A
Time
Graph(s)
moving at a steady speed
stationary (not moving)
moving fastest
changing speed
Table 2.03
Original material © Cambridge University Press 2017
Time
Cambridge IGCSE Combined and Co-ordinated Sciences
b Table 2.04 shows the distance travelled by a runner during a 100 m race. Use the data to draw a
distance–time graph on the graph paper grid provided.
Distance / m
0
10.0
25.0
45.0
65.0
85.0
105.0
Time / s
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Table 2.04
12
Now use your graph to answer these questions:
How far did the runner travel in the first 9.0 s? How long did the runner take to run the first 50.0 m? How long did the runner take to complete the 100 m? Use the gradient of your graph to determine the runner’s average speed between 4.0 s and 10.0 s.
On your graph, show the triangle that you use.
c On the graph paper grid provided, sketch a distance–time graph for the car whose journey is described here:
•
The car set off at a slow, steady speed for 20 s.
•
Then it moved for 40 s at a faster speed.
Original material © Cambridge University Press 2017
Chapter P2: Describing motion
•
Then it stopped at traffic lights for 20 s before setting off again at a slow, steady speed.
d The graph represents the motion of a bus for part of a journey.
1000
Distance / m
800
13
600
400
200
0
0
20
40
60
80
100
Time / s
On the graph, mark the section of the journey where the bus was moving faster.
From the graph, calculate the following:
•
the speed of the bus when it was moving faster
•
the average speed of the bus.
Original material © Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Exercise P2.05 Acceleration
When an object changes speed, we say that it accelerates. Its acceleration is the rate at which its
speed increases.
a In an advertisement, a car is described like this:
“It can accelerate from 0 km/h to 80 km/h in 10 s.”
By how much does its speed increase in each second (on average)? b A cyclist is travelling at 4.0 m/s. She speeds up to 16 m/s in a time of 5.6 s. Calculate her acceleration.
14
c A stone falls with an acceleration of 10.0 m/s2. Calculate its speed after falling for 3.5 s.
d On the Moon, gravity is weaker than on Earth. A stone falls with an acceleration of 1.6 m/s2. How long will it take
to reach a speed of 10 m/s?
Original material © Cambridge University Press 2017
Chapter P2: Describing motion
Exercise P2.06 Speed–time graphs
In this exercise, you draw and interpret some speed–time graphs. You can calculate the
acceleration of an object from the gradient (slope) of the graph. You can calculate the distance
travelled from the area under the graph.
a The diagrams A–D show speed–time graphs for four moving objects. Complete Table 2.05 by indicating
(in the second column) the graph or graphs that represent the motion described in the first column.
Time
D
Speed
C
Speed
Speed
B
Time
Description of motion
Speed
A
Time
Time
Graph(s)
moving at a steady speed
speeding up, then slowing down
moving with constant acceleration
accelerating to a steady speed
Table 2.05
15
b The graph represents the motion of a car that accelerates from rest and then travels at a steady speed.
Speed / m/s
30
20
10
0
0
10
20
30
Time / s
Original material © Cambridge University Press 2017
40
Cambridge IGCSE Combined and Co-ordinated Sciences
From the graph, determine the acceleration of the car in the first part of its journey.
On the graph, shade in the area that represents the distance travelled by the car while accelerating.
Label this area A.
Shade the area that represents the distance travelled by the car at a steady speed. Label this area B.
Calculate each of these distances and the total distance travelled by the car.
1
[Note: area of a triangle = × base × height.]
2
c On the graph paper grid, sketch a speed–time graph for the car whose journey is described here:
16
•
The car set off at a slow, steady speed for 20 s.
•
Then, during a time of 10 s, it accelerated to a faster speed.
•
It travelled at this steady speed for 20 s.
•
Then it rapidly decelerated and came to a halt after 10 s.
Original material © Cambridge University Press 2017
Chapter P3
Forces and motion
KEY TERMS
force: the action of one body on a second body that causes its velocity to change
resultant force: the single force that has the same effect on a body as two or more forces
mass: the property of an object that causes it to resist changes in its motion
weight: the downward force of gravity that acts on an object because of its mass
USEFUL EQUATIONS
Force = mass × acceleration
F = ma
Exercise P3.01 Identifying forces
Forces are invisible (although we can often see their effects). Being able to identify forces is an
important skill for physicists.
The pictures show some bodies. Your task is to add at least one force arrow to each body, showing a force acting
on it. (Two force arrows are already shown.)
17
Each force arrow should be labelled to indicate the following:
•
the type of force (contact, drag/air resistance, weight/gravitational, push/pull, friction, magnetic)
•
the body causing the force
•
the body acted on by the force.
For example: the gravitational force of the Earth on the apple.
Original material © Cambridge University Press 2017
17
Cambridge IGCSE Combined and Co-ordinated Sciences
Exercise P3.02 The effects of forces
A force can change how a body moves, or it may change its shape.
a Each diagram shows a body with a single force acting on it. For each, say what effect the force will have.
A
B
C
D
18
b A boy slides down a sloping ramp. In the space below, draw a diagram of the boy on the ramp and add a
labelled arrow to show the force of friction that acts on him.
What effect will the force have on the boy’s movement?
Original material © Cambridge University Press 2017
Chapter P3: Forces and motion
Exercise P3.03 Combining forces
When two or more forces act on a body, we can replace them by a single resultant force that has
the same effect.
a In Table 3.01, the left-hand column shows four objects acted on by different forces. For the same objects in the
right-hand column, add a force arrow to show the resultant force acting on it in each case.
80 N
N
80
80 N
8080
NN
45 N
N
45
45 N
4545
NN
60 N
N
60
8060
NN
50
N
6050
NN
60
50 N
5050
NN
60 N
40 N
N
40
4540
NN
4040
NN
Forces on object
Resultant force
20 N
N
20
40 N
20 N
2020
NN
20
N
4520
NN
20 N
20 N
20 N 20 N
50
N
20
N
8020
NN
20 N
2020
NN
40 N
N
40
40 N
40 N20 N
20 N
N
50 N 20 N 4040
40NN
N
20 N
40
20 N
40 N
2020
N N 4040
N
20 N N
80
N
NN
100
N
100
N
40 N 45
100 N
100
100 N
100 N
100
NN
100
N
100
20100
N 20
NN
N
40 N 20
60 N
60 N
100 N
N
40 N
100
100100
N N
100
N
40100
N N
100 N
50 N
Table 3.01
20 N
2040NN
100draw
N
b In the space below,
a diagram showing a body with four forces acting on it. Their resultant must be 4 N
acting vertically downwards.
20 NN
100
20 N
100
N
40 NN
100
20 N
100 N
40 N
100 N
100 N
Original material © Cambridge University Press 2017
19
Cambridge IGCSE Combined and Co-ordinated Sciences
Exercise P3.04 Mass and weight
Mass and weight are two quantities that can easily be confused.
How well do you understand the difference between mass and weight? In the second column of Table 3.02, write
‘mass’ or ‘weight’ (or ‘both’), as appropriate.
Description
Mass or weight or both?
a force
measured in kilograms
measured in newtons
decreases if you go to the Moon
a measure of how difficult it is to accelerate a body
caused by the attraction of another body
increases if more atoms are added to a body
balanced by the contact force of the floor when you are standing
used in calculating the acceleration of a body when a force acts on it
makes it difficult to change the direction of a body as it moves
decreases to zero as a body moves far from the Earth or any other object
Table 3.02
20
Exercise P3.05 Force, mass and acceleration
Here you practise using the relationship F = ma.
a The equation F = ma relates three quantities. Complete Table 3.03 to show the names of these quantities and
their SI units.
Quantity
Symbol
SI unit
F
m
a
Table 3.03
b Rearrange the equation F = ma to change its subject:
m=
a=
c Calculate the force needed to give a mass of 20 kg an acceleration of 0.72 m/s2.
Original material © Cambridge University Press 2017
Chapter P3: Forces and motion
d A car of mass 450 kg is acted on by a resultant force of 1575 N. Calculate its acceleration.
e One way to find the mass of an object is to apply a force to it and measure its acceleration. An astronaut
pushes on a spacecraft with a force of 200 N. The spacecraft accelerates at 0.12 m/s2. What is the mass of the
spacecraft?
f
In the space below, draw a falling stone with the following forces acting on it:
•
its weight, 8.0 N
•
air resistance, 2.4 N.
g Calculate the stone’s acceleration. (Its mass is 0.80 kg.)
Original material © Cambridge University Press 2017
21
Answers
Example answers and all questions were written by the author.
Chapter P1 Making measurements
For example, the table should resemble the following
(see Table A1.01):
Exercise P1.01 The SI system of units
Measurement
short side
long side
diagonal
a metre (m)
cubic metre (m3)
12.5
17.3
21.3
156
299
454
(short side)2 + (long side)2 = 156 + 299 = 455
millimetre (mm)
f
c 100
Comments will vary.
Exercise P1.03 Density data
1000
d For example: inch, foot, yard, mile, furlong, etc.
e For example: to make it easier to compare measurements;
to make it easier to share data
f
Length2 / cm2
Table A1.01
b kilometre (km)
122
Length / cm
a see Table A1.02
b cork
c
For example: medicine (doctors, nurses), engineering,
architecture and surveying, etc.
Exercise P1.02 Accurate measurements
a
olive oil
6.7 cm
Align end with zero; place next to ruler; straighten it out.
water
b–e Answers will depend on the piece of paper selected by the
student.
Material
water
ethanol
olive oil
mercury
ice
diamond
cork
chalk
iron
tungsten
aluminium
gold
State / type
liquid / non-metal
liquid / non-metal
liquid / non-metal
liquid / metal
solid / non-metal
solid / non-metal
solid / non-metal
solid / non-metal
solid / metal
solid / metal
solid / metal
solid / metal
Density / kg/m3
1 000
800
920
13 500
920
3 500
250
2 700
7 900
19 300
2 700
19 300
Table A1.02
122
Original material © Cambridge University Press 2017
Density / g/cm3
1.000
0.800
0.920
13.500
0.920
3.500
0.250
2.700
7.900
19.300
2.700
19.300
Answers
Quantity
SI unit (name and symbol)
Non-SI units
Measuring instrument
distance
metre (m)
mile, etc.
tape measure, rule
time
second (s)
hour, etc.
clock, stopwatch
speed
metre per second (m/s)
mile per hour, etc.
Table A2.01
d Disagree. Aluminium (metal) is less dense than diamond
(non-metal). But it is true that, for the table, most metals
are more dense than most non-metals.
Exercise P2.02 Speed calculations
a The green car should be circled as the fastest in Table A2.02
e 57.9 kg
Car
f
red car
green car
4.2
23.8
3.8
26.3
yellow car
4.7
21.3
19 300 kg/m3
possibly tungsten
Exercise P1.04 Testing your body clock
Time taken / s
Speed / m/s
Table A2.02
b 1 200 000 m
Answers will vary.
tudents should recognise that measuring 50 pulses
S
is better than measuring 10 (provided that the pulse rate is
not changing). Also they should appreciate that pulse rate
can change, and that this makes it less reliable than
using a pendulum.
80 min
4800 s
250 m/s
c 10 m/s
15 m/s
Chapter P2 Describing motion
Exercise P2.1 Measuring speed
a see Table A2.01
a 770 m
distance
c 3.60 s
time
8.0 s
2.8 m/s
d 2.0 m
c Knowing the distance between the detectors,
calculate
Exercise P2.03 More speed calculations
b 40 s
b distance travelled
speed =
It is speeding up (accelerating).
Their speeds might change during the race.
distance
time
24 m/s; within the speed limit
0.048 s
d If the time taken by a vehicle is equal to or less than 0.048 s,
the warning lights are shown.
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123
Cambridge IGCSE Combined and Co-ordinated Sciences
Exercise P2.04 Distance–time graphs
Exercise P2.05 Acceleration
a see Table A2.03
a 8 km/h
Description of motion
Graph(s)
moving at a steady speed
B, D
stationary (not moving)
A
moving fastest
B
changing speed
C
b 2.1 m/s2
c 35 m/s
d 6.25 s
Exercise P2.06 Speed–time graphs
Table A2.03
a see Table A2.04
b
Description of motion
100
Distance / m
80
60
C
speeding up, then slowing down
A
moving with constant acceleration
D
accelerating to a steady speed
B
b 1.6 m/s2
20
0
moving at a steady speed
Table A2.04
40
124
Graph(s)
0
2
6
4
8
10
12
30
Speed / m/s
Time / s
75.0 m
6.5 s
11.5 s
20
B
10
A
10.0 m/s
0
c
0
10
30
20
40
Time / s
Distance
A=
1
× 15 × 24 = 180 m
2
B = 25 × 24 = 600 m
total distance = 780 m
0
0
20
40
60
80
100
c
d first section marked as faster
Speed
Time / s
17.5 m/s
10.0 m/s
0
0
10
20
30
Original material © Cambridge University Press 2017
40
Time / s
50
60
70
Answers
Chapter P3 Forces and motion
Exercise P3.01 Identifying forces
Forces and labels should be as follows:
Apple: (up) air resistance of air on apple;
(down) gravitational force of Earth on apple
Car: (up) contact force of road on car;
(down) gravitational force of Earth on car;
(back) air resistance of air on car; (forwards) push of engine on car
Person on slide: (down) gravitational force of Earth on
person; (up slope) frictional force of slide on person;
(normal to slope) contact force of slide on person
Fish: (down) gravitational force of Earth on fish;
(up) upthrust of water on fish; (back) drag of water
on fish; (forwards) thrust caused by fish’s movements, acting on
fish
Paperclip: (down) gravitational force of Earth on clip;
(up) magnetic force of magnet on clip
Box: (down) gravitational force of Earth on box;
(up) contact force of floor on box; (to right) push of
person on box; (to left ) frictional force of ground on box
Original material © Cambridge University Press 2017
125
Cambridge IGCSE Combined and Co-ordinated Sciences
Exercise P3.02 The effects of forces
Exercise P3.04 Mass and weight
a A
Van will accelerate / speed up
See Table A3.02
B Van will decelerate / slow down
Description
Mass or weight
or both?
a force
weight
measured in kilograms
mass
measured in newtons
weight
decreases if you go to the Moon
weight
a measure of how difficult it is to
accelerate a body
mass
C
Tree will bend over to right
D Ball will accelerate downwards (but follow a
curved path)
b
caused by the attraction of another body weight
increases if more atoms are added to
a body
both
balanced by the contact force of the
floor when you are standing
weight
used in calculating the acceleration of
a body when a force acts on it
mass
makes it difficult to change the
direction of a body as it moves
mass
Exercise P3.03 Combining forces
decreases to zero as a body moves far
from the Earth or any other object
weight
a see Table A3.01
Table A3.02
Friction will make him go slower (better: … reduce his
acceleration).
126
Forces on object
Resultant force
80 N
45 N
35 N
Exercise P3.05 Force, mass and
acceleration
60 N
40 N
30 N
a see Table A3.03
50 N
20 N
20 N
20 N
Quantity
Symbol SI unit
force
F
newton (N)
mass
m
kilogram (kg)
acceleration a
20 N
Table A3.03
40 N
20 N
100 N
40 N
metre per second squared (m/s2)
b m=
100 N
a=
40 N
F
2.4 N
a
F
m
c 14.4 N
100 N
d 3.5 m/s2
Table A3.01
b Diagrams will vary; but must show a body with four forces
acting on it with resultant 4 N acting vertically downwards.
e 1667 kg (1670 kg)
f
see diagram on right side.
g 7.0 m/s2
Original material © Cambridge University Press 2017
8.0 N