CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
Exam-style questions and sample answers have been written by the authors. In examinations, the way marks are awarded
may be different.
Practical Workbook
answers
Chapter 1
Practical investigation 1.1:
Estimating measurements
Practical investigation 1.2:
The simple pendulum
Getting started
Getting started
Measurement Equipment
For a short time frame, measure over multiple
oscillations, for example, ten, and record the
time for this. The reaction time for a human is
approximately 0.4 s. This would affect the time if
done for one oscillation. Use a fiducial marker to
be able to take time from a consistent point.
length
ruler
volume
measuring cylinder, ruler, beaker
mass
balance
time
timer, stopwatch
Answers to workbook questions
1
Learners record their results in the table.
1
Learners should record their results in the table.
2
2
Learners should check that all measurements
are to the correct number of significant figures.
Learners calculate the time period for each
length of pendulum by dividing their time
period for ten oscillations by 10.
3
Learners calculate average values for
each measurement.
3
4
Learners comment on their estimated and
measured results. They should make
reference to the limits of accuracy of the
measuring equipment.
Learners draw their graphs, with length on the
horizontal axis and time period on the vertical
axis, to produce a roughly horizontal line.
4
Results should show that as the length of the
pendulum increases, the time period of the
swing increases.
5
Learners calculate the volume of the glass
block, based on their measurements
using rulers.
5
The mass of the pendulum may have an
effect or the type of material from which the
pendulum is made.
6
A pair of vernier callipers would give a more
precise result than a ruler. This increased
degree of accuracy would then be carried into
the calculation. Learners suggest alternative
methods of measurement.
Practical investigation 1.3:
Calculating the density of liquids
7
1
Answers to workbook questions
30 cm ruler precision is correct to 1 mm; metre
ruler precision is correct to 1 mm; stopwatch
precision is correct to 0.01 s.
Getting started
Density of a fluid can help to tell whether an
object will float. This is important in relation to
aerospace and shipping.
Volume of fluid: 45 cm3, 72 cm3, 7 cm3.
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
Answers to workbook questions
1
Learners record their results in the table.
2
Learners sketch their graphs of mass (vertical
axis) against volume (horizontal axis) for each
of the liquids.
3
Learners draw and label the line of best fit on
each graph.
4
The graph that has the steepest gradient will
have the highest density. The gradient of the
saltwater solution is the steepest, showing
that saltwater has the highest density of all
the solutions.
iv
c
Chapter 2
Practical investigation 2.1:
Average speed
Water 1 g/cm3, oil 0.92 g/cm3,
saltwater 1.03 g/cm3.
6
Saltwater solution, water, oil (bottom to top).
•
7
Learners should suggest reasons, for example
errors in measurement, errors in calculations.
•
8
The learner is incorrect. Results from this
investigation show that oil is less dense than
saltwater so would float on the surface of
the saltwater.
Getting started
Answers to exam-style questions
a
b
c
Eye level with 8 cm3 line [2]
8 cm3 [1]
m 65.01
i
= __
​​  v ​,​ _____
​​   ​​ [1], 8.13 [1] g/cm3 [1]
8
ii Steel [1]
Using the data from the table, none of the
metals will float. [1] For a metal to float it
will need a density less than [1] water. This
would mean a value below 1 g/cm3.
i
ii
a
1
Learners record their results in the table.
2
Learners use the data from their table to plot a
distance–time graph of their results.
3
The section with the steepest gradient
represents the section in which the runner was
moving fastest, as the gradient represents the
speed / the section with the smallest increase in
time represents the section in which the runner
was moving fastest as they covered the 20 m in
a smaller amount of time.
4
The triangulation method or change in
vertical or horizontal values should be
d
evident, or evidence of using v = __
​​   ​​ provided.
t
Check learners’ results.
5
Calculate the distance travelled and the time
taken in an instant. This would be difficult
to measure.
6
total distance travelled
​
Average speed = ____________________
​
total time taken
7
100
= _____________
​ ​   ​​
learner answer
Precision is dependent on the instruments
used. Precision can be increased by using
instruments with smaller divisions.
i and ii
Quantity
Measuring device
Resolution
distance
metre ruler;
measuring tape
1 mm;
1 mm
time taken
stopwatch; timer
0.01 s
b
i
ii
iii
2
1 cm : 5 cm scale; radius of the track
15 cm [1]
Circumference = 2πr = 2π × 15
= 94.2 cm [1]
She should record all values to the
same number of significant figures. [1]
0.49 s [1]
Difficulty seeing the start of the run, or
missing the runner pass the line.
Ask runners to repeat their runs, or ask the
starter to move their arm as they say, ‘Go’.
Answers to workbook questions
[Total: 10]
2
She could record the time taken for
multiple laps so there is no impact from
human reaction time. [1] She could use a
light gate to record the time. [1]
[Total: 12]
5
1
distance ____
94.2
Average speed = ________
​​
​​; = ​​
​​ [1]
0.49
time
= 192 cm/s [1]
8
Immediately the starter signals the
runner to start to move, the timers start
their stopwatches.
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CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
9
The graph would appear as a curve with an
increasing gradient. The curve would get
steeper as time went on.
Practical investigation 2.2:
Speed–time graphs using
ticker tape
Getting started
Time between dots: ___
​​  1  ​​ = 0.02 s
50
Time period for ten spaces: 0.2 s
Answers to workbook questions
1
Learners should cut the ticker tape into
ten‑dot sections, labelling them in the order in
which they are cut from the start of the tape.
2
Refer to the example of a velocity–time graph
in exemplar data on Cambridge GO.
3
Refer to the example of a velocity–time graph
in exemplar data on Cambridge GO .
4
See learners’ graphs.
5
Columns are increasing in height; there is a
positive gradient so the velocity is increasing.
6
See learners’ graphs.
7
Learners calculate the gradients of their
graphs; units cm/s2. This represents
the acceleration.
8
Learners calculate the area under their graphs;
units cm.
9
Started counting the dots from where a
pattern was visible, started counting where
the gaps were clear, used a fresh carbon
paper disc.
10 The ramp is not steep enough so the trolley
has moved at a constant velocity. Increase the
gradient of the ramp.
11 This graph would show the acceleration of the
vehicle over a short period of time, using the
distance travelled.
Answers to exam-style questions
1
a
Check suitable scale has been chosen [1];
axes should be labelled, including units
1
[1]; correct plot to _​​ 2 ​​ square [2]; line of best
fit drawn. [1]
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
cm 25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
b
c
d
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Triangulation method [1]; 1.2 [1]; m/s2 [1]
1
​​ _2 ​​× base × height visible [1]; 1.5 [1]; m [1]
Not correct. [1] Reason: a straight-line
graph represents constant acceleration. [1]
[Total: 13]
3
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
Chapter 3
Practical investigation 3.1:
Estimating the acceleration
of freefall
Getting started
Gravity becomes weaker the further away from the
surface of the Earth. This means the acceleration
due to free fall will be smaller.
Calculations will depend on learners’ researched
values for g.
Answers to workbook questions
4
Practical investigation 3.2:
Investigating the relationship
between force, mass
and acceleration
Getting started
Situation
How will you prevent
it?
Starting point of the
trolley changing
Make a line on the
runway and always
start from this point
End point of the
trolley changing
Make a line on the
runway and always
end at this point
Recording the time
incorrectly
Take repeats and
calculate an average
1
Learners record their results in the table.
2
Learners plot a graph of their results to
calculate the acceleration of free fall.
3
Learners draw in a line of best fit on
their graph.
4
A value in the region of 10 will be acceptable
for the gradient.
5
The acceleration of free fall should
approximate to 10. Learners will need to
make a comparative statement between their
value and the official value such as: ‘The value
of my gradient was 11. This is close to the
accepted value but slightly higher.’
Sensible suggestion for why the value is
different, for example: I might have misread
the scale on the newton meter; the newton
meter did not show zero when no mass was
hanging from it.
1
Learners record their results for increasing the
number of elastic bands in the table.
2
Learners record their results for increasing the
mass in the table.
3
As the force on the trolley increases, the
acceleration increases. This is shown in the
results by the trolley covering the distance
in a shorter period of time when the force is
greater. (Learners should use their data to
support this.)
6
Yes, a straight-line graph was obtained,
which shows that the acceleration of free fall
is constant.
4
7
0.01 N for newton meter; 00.1 g. Top-pan
balances have a precision of about 1 g
to 0.01 g.
As the mass of the trolley increases the
acceleration decreases. This is shown in the
results, by the trolley covering the distance
in a longer period of time as the mass of the
trolley increases. (Learner should use their
data to support this.)
5
Control variables could be: force investigation
– the mass of the trolley; mass investigation –
the number of elastic bands, or the distance by
which the bands are pulled.
6
Repeat the results and calculate an average.
Results should be similar for them to
be reliable.
Reset its position
Trolley colliding with
away from the sides
the side of the runway at the beginning of
every run
Answers to workbook questions
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
Practical investigation 3.3:
Momentum in explosions
Getting started
Value
Value rounded to 2 s.f.
25 478
25 000
679
680
1.23
1.2
0.056 78
0.057
0.000 657 4
0.000 66
Answers to workbook questions
Practical investigation 4.1:
The weighing machine
Getting started
Possible methods: use a set-square; measure the
height of the ruler at three different points.
Answers to workbook questions
1
Learners calculate and record the moment
and the mass for each object, recording their
results in the table.
2
Learners weigh the masses and record their
results in the table.
1
Learners record their results in the table.
2
Learners calculate the momentum of the
trolleys and add the answers to the table.
3
Yes or no. Data from the learners’ results
should be used to support their answer.
3
As velocity and momentum are vector quantities
they have both magnitude and direction.
4
4
The momentums of trolley A and of trolley B
are equal in magnitude and opposite in
direction. This can be seen by looking at the
results in the table (should quote a result from
table to support).
Any two suggestions from: ensure that the
ruler is horizontal; take readings at eye level
to reduce parallax error; use a set square to
ensure that the ruler measuring the height of
the ruler is perpendicular to the bench.
5
The height of the ruler from the bench was
measured at three different points to ensure
they were all the same.
6
This ensures that the ruler is horizontal and
thus the forces act at right angles to the rule.
5
Learners should repeat the investigation for
each trolley mass and calculate an average of
the results.
Answers to exam-style questions
1
a
b
c
5
Chapter 4
change in velocity
________________
​​ [1]
i
Acceleration =
​​
time
ii Measure the change in velocity of
the trolley. [1]
i
Independent variable: force; dependent
variable: change in velocity [1]
ii Control variable: the mass of
the trolley [1]
Suitable scale required [1]; axes labelled
1
including units [1]; correct plot to ​​ _2 ​​ square
[2]; line of best fit. [1]
ii The acceleration is directly
proportional to the force applied [1];
the graph is a straight line through
(0, 0). [1]
iii Evidence of triangulation method
[1]; mass approximately 500 [1] g [1]
or 0.5 kg (depending on the type of
trolley used)
[Total: 15]
Practical investigation 4.2:
Finding the centre of gravity
Getting started
Learners should research a method. A common
method is to hang the two-dimensional shape from
three different positions and draw a vertical line
through each point of suspension with the help
of a plumb line. Other sensible suggestions
are possible.
Answers to workbook questions
1
Learners draw three vertical lines through
different points of suspension; the lines should
meet in one point.
2
To improve the accuracy: wait until the
plumb-line comes to rest; use a stiffer piece
of string or maybe a rod for the plumbline; make sure the card is at eye level when
drawing the lines.
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
Practical investigation 4.3:
Tower stability
d
i
Getting started
Answers will be relevant to the learner and
their equipment.
ii
Answers to workbook questions
Example method
1
Measure the height of the centre of gravity of
the block and record it in a table.
2
Place the block on the ramp.
3
Increase the incline of the ramp until the
block topples.
4
Use a protractor to measure the angle at
which it topples and record it in the table.
5
Repeat twice more and record in your table.
6
Calculate the average (mean) result.
7
Repeat steps 1–6 for a blocks with a range
of heights.
Questions
1 Learners record their results in the table.
[Total: 13]
Chapter 5
Practical investigation 5.1:
Determining the spring constant
Getting started
•
•
Taking measurements from the same point
every time reduces the chance of error in
measurement of length and extension and
keeps measurements consistent.
Learners will need to adapt their equipment
accordingly so answers may differ. A suggestion
might be to use a fiducial marker, for example,
use a pin on the selected end point of the
spring so it is clearly indicated on the ruler.
Allow time for the spring to settle before
recording the extension.
2
Learners plot a graph of the angle of topple
against the height of the centre of mass.
3
Learners draw a line of best fit on their graphs.
4
Yes – as the height of the centre of mass
increases the angle of topple gets smaller.
The learner should include key points from
graph to support their answer.
Answers to workbook questions
1
Learners complete the table with their
own results.
5
Answers could include: the width of the base of
the blocks; the starting position of the blocks.
2
Learners plot a graph of load against
extension with appropriate labels and scales.
6
Keep the blocks in the same orientation
throughout. The starting position on the ramp
was kept the same throughout.
3
Learners join the points with a line of best fit.
4
Check learners’ graphs for anomalies.
5
It should be a straight-line graph through
the origin.
6
The triangulation method should be used to
calculate the spring constant of the graph.
Answers to exam-style questions
7
i
x = 1.5 cm [1]
ii y = 2.0 cm [1]
x = 15 cm; y = 20 cm [2]
The graph would begin to curve as masses
were added to the spring.
8
The change in shape would occur because the
spring has been permanently deformed by the
applied load.
7
Ruler: 1 mm; protractor: 1°.
8
Precision could be improved by using smaller
divisions of measurement.
1
a
b
iEvidence of principle of moments [1];
1.53 [1]; N [1]
ii 153 [1] g [1] (or 0.153 [1] kg [1])
c
6
Any two reasons from: the learner
might not have read the newton
meters correctly; there were rounding
errors in calculation; difficulty
balancing a small object; the object
may not have uniform density. [2]
Take readings either side of the object
or mark the object with a central line
and align with the ruler marking. [2]
•
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
9
One reason from: the spring was still
oscillating when the load was applied; not
taking readings at eye level (parallax error);
the ruler is not at right angles to the bench; the
ruler is not aligned with the spring correctly;
readings were taken from the wrong points.
10 Use a set square to ensure that the ruler is
correctly positioned and clamped in place.
Chapter 6
Practical investigation 6.1:
Gravitational potential energy
Getting started
Practical investigation 5.2:
Calculating pressure
•
•
•
•
Getting started
Answers to workbook questions
force
Pressure = _____
​​  area ​​
1
Learners record their measurements.
2
Learners calculate the g.p.e. for the
heights used.
3
Learners plot the graph of gravitational
potential energy (vertical axis) against height
(horizontal axis) and draw a line of best fit.
4
As the height increases so does the g.p.e. This
is represented by a straight-line graph with
positive gradient, passing through the origin.
The height and g.p.e. are in direct proportion.
5
Look for evidence of the triangulation
method. The gradient should be
approximately equal to the measured mass of
the ball × 10, in newtons / N.
6
Weight = measured mass × 10 / N. Differences
will come from errors in measurement, such
as placing the string incorrectly, misreading
the length of string against the ruler, any other
sensible suggestion.
7
Measure a height and mark it with chalk.
Release the ball from this point.
Order: high-heeled (stiletto) shoes; sitting on a
stool; desk on a floor; standing on one foot; a
walking elephant.
Answers to workbook questions
1–6 Answers will depend on learner measurements.
7
Learners should compare their calculations to
their estimates in the ‘Getting started’ section.
8
The stiletto provides an area 1000 times
smaller than the area provided by an
elephant’s foot. Whilst the force of an
elephant is much greater than that of a
human, it is spread over a greater area and so
reduces the pressure exerted on the ground.
9
Use a sharp pencil and ensure the point is held
very close to the object when drawing
Answers to exam-style questions
1
a
b
c
d
From the top of the spring to the bottom
of the spring, or from the same point on
the top loop to the same point on the
bottom loop. [1]
Load / N [1]; Length / m [1];
Extension / m [1]
Suitable scale required [1]; axes labelled
1
including units [1]; correct plot to _​​ 2 ​​ square
[2]; line of best fit drawn. [1]
i
Yes [1]; reason: it is a straight line
through the origin [1]
ii Use a set square and clamp the
ruler. [1]
[Total: 12]
7
0.05 m
0.32 m
0.65 m
0.87 m
•
•
•
•
26 cm
34 cm
76 cm
92 cm
Practical investigation 6.2:
Kinetic energy
Getting started
Learner discussion. Issues that might arise include:
standing position at the start and end; keeping the
same person for rolling the ball; keeping the same
ball; making sure the timer is directly above the
finish line.
Answers to workbook questions
1
Learners record the mass of the ball in
the table.
2
Learners calculate the average speed of the
ball over 5 m.
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CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
3
Learners calculate the square of the speed and
the k.e., recording their results in the table.
4
Learners plot the graph of kinetic energy
(vertical axis) against the square of the speed
(horizontal axis) and draw a line of best fit.
5
They are directly proportional. The graph is a
straight line, passing through the origin.
As the speed increases, the kinetic energy also
increases. Data from the graph or the learners’
results should be quoted in support.
6
The difficulty might be in measuring time
exactly. To improve the results, stand over
the line and stop the stopwatch as the ball
crosses it. Use light gates, use video recording
equipment and slow motion.
7
Reliability could be improved by repeating
each roll and finding the average
8
Use balls of differing masses and calculate
their k.e. using a constant force to roll the ball.
Practical investigation 6.3:
Energy and the pendulum
Getting started
•
•
The principle of conservation of energy states
that energy cannot be created nor destroyed,
only transferred from one form to another.
As the starting height of the pendulum
increases, the velocity at the lowest point will
increase. Thus, as the starting amount of g.p.e.
increases, the k.e. gained as it falls increases.
Answers to workbook questions
1
Learners record the mass of the pendulum
bob in the table.
2
Learners calculate the average velocity for
each height of the pendulum.
3
Learners calculate and record the g.p.e. and
the k.e. for each height.
4
Learners plot the graph of k.e. against g.p.e.
for each height and draw in a line of best fit.
5
As the g.p.e. increases the k.e. also increases, in
proportion. Learners should use data from the
graph to support this. The graph is a straight
line through the origin,
6
8
Circle any anomalous result and omit it from
the calculation of the average.
7
i
ii
A data-logger can be used to measure the
velocity to a high degree of precision.
The experiment is repeated and the
average calculated.
Answers to exam-style questions
1
i
ii
iii
0.60 m [1]
Ignore any anomalous results. [1] Add the
values together and divide by the number
of values in the addition. [1]
1.04, 0.92, 0.75, 0.56, 0.46 [3 marks
all, 2 marks for 4 correct, 1 mark for
3 correct]
[Total: 6]
Chapter 7
Practical investigation 7.1:
Solar panels
Getting started
Learners’ answers will vary depending on the
values they set.
Answers to workbook questions
1
Learners prepare their tables and record
their data.
2
As the area of the solar panel increases,
the greater the temperature rise. Therefore,
the greater the area, the faster it heated up.
Learner data should be referenced.
3
If the volume was different in each container
it would affect the results. The more water
used, the longer the time it will take to heat up
so this would affect the results.
4
The intensity of light on each solar panel will
not be the same. The panel with the lowest
light intensity will take longer to warm up.
Practical investigation 7.2:
Solar buggies
Getting started
•
•
•
Dependent variable: distance travelled by
the car.
Independent variable: distance from the
light source.
Control variables: type of solar buggy;
surface; starting position; colour of the light.
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
Answers to workbook questions
Answers to exam-style questions
1
1
Learners prepare their tables and record data.
Headings and units should be included in the
table. An example could be:
Distance from the
light source / m
Distance travelled
/m
2
Learners should use their data to draw a graph
of distance from the light source (m) against
distance travelled (m).
3
As the distance from the light source increases,
the distance travelled by the buggy also
increases. Learners should refer to their data.
4
Learners refer to their data and results to
assess whether their prediction is supported.
5
Control variables: light intensity – The colour
of the light was kept the same, and the same
bulb was used.
Practical investigation 7.3:
Efficiency of a tennis ball
Getting started
Challenges identified by learners may include
ensuring the ball is released from the same height
– use a marker; or that it is released with the same
force – same person to release it each time.
Answers to workbook questions
9
a
b
1
Learners record their answers in the table.
2
Learners calculate the average rebound height.
3
Learners calculate the efficiency of
the bounce.
4
c
26.5 [1]; 31 [1]; 35.5 [1]
Any of: read at eye level to reduce
parallax error; repeat results and calculate
average or spot anomalous results; use a
light meter to check the intensity, measure
the intensity; check for zero error,
calibrate thermometer [2]
i
360 seconds [1]; misreading
thermometer (or any other sensible
suggestion) [1]
1
ii Correct plot to _​​ 2 ​​ square [2]; line of
best fit drawn [1]; neatness of plot and
line of best fit – all should be clear [1]
iii The greater the intensity, the greater
the temperature rise in the same
time interval [1]; learner data
to support [1]
[Total: 13]
Chapter 8
Practical investigation 8.1:
Work done
Getting started
Learners should label the requested distances on
the diagrams to show where they will take their
measurements from and discuss general ideas on
keeping their measurements accurate, such as line
of sight, and start and end markers.
Answers to workbook questions
1
Learners record their results in the table.
2
Learners calculate and record the weight lifted.
As the drop height increased the rebound
height increased. The line of best fit is straight
so the efficiency has remained constant.
3
Learners calculate and record the upwards
distance travelled.
4
Learners calculate and record the work done.
5
Efficiency is a ratio of the two connected values.
5
6
This will ensure that the drop height and the
rebound height are measured as close to the
true value as possible.
The shoulder raise transfers the most energy.
Reason: the weight/force is moved through
the greatest distance so will require the
most energy.
7
Examples of errors include: parallax error
– read off the ruler from eye level; dropping
from the wrong height – double check the
starting height each time; judging the rebound
height when the ball is moving; measuring the
starting and rebound heights from the same
point on the ball
6
Taking readings on a metre ruler at eye level
reduces parallax error, improving the accuracy
of the measurement.
7
Learners might not have moved the weight the
whole distance and so the value calculated for
work done will be too great.
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8
When the masses are moving upwards the
muscles are doing work against gravity.
9
Top-pan balance precision is ±1 g (will depend
on the balance used in class); ruler precision is
±1 mm.
b
Practical investigation 8.2:
Calculating mechanical power
Getting started
•
•
energy transferred
Power = ________________
​​
​​
time taken
Learners can measure the work done over a
period of time. This would include measuring
distances travelled in the direction of the force.
Headings [1]; correct units [1]
Correctly calculated work done [2]
Surface
Distance
travelled
/m
Force
applied
/N
Work
done / J
table top
0.5
0.8
0.4
sandpaper
0.5
2.5
1.25
wooden
bench
0.5
1.8
0.9
paper
0.5
1.2
0.6
c
i
Answers to workbook questions
ii
Power / W
Work done / J
Time taken / s
Depth of
1 squat / m
Total distance
travelled / m
Weight / N
Mass / kg
Learners should produce a table similar to the
one below and record their results.
Name
1
The learner should ensure that the
newton meter is pulling at right angles
to the tub. The learner should take
the meter reading at eye level. (Accept
any sensible suggestion.) [1]
The learner can attach a pulley to
the tub. [1] As she adds masses to the
pulley she can record the mass that
causes the tub to move and calculate
the force from here. [1]
[Total: 9]
Chapter 9
2
Learners calculate the work done for
each learner.
3
Learners calculate and record the power
generated for each learner.
4
Answer correct, and in line with experimental
results. The answer should reference the most
energy transferred / work done.
5
10
No. The total work done depends on the
distance travelled, not just the weight of the
learner. The time it takes to complete the
work done will determine the power. Learners
would not be able to determine this by looking
at the subject’s weight alone.
Practical investigation 9.1:
Changes of state of matter
Getting started
Liquids
Gases
Bonds
between
particles
weak
no real bonds
Movement of
particles
glide over one random
another
haphazard
motion
Relative
kinetic energy
lower
higher
Answers to workbook questions
Answers to exam-style questions
1
Learners record their results in the table.
1
2
Small bubbles start to rise, as air escapes, then
larger bubbles form.
3
Large bubbles, steam escapes from the surface,
temperature close to 100 °C. The temperature
does not rise above 100 °C.
4
The temperature remains constant.
a
0.8 N, 2.5 N, 1.8 N, 1.2 N (1 mark awarded
for each correct figure, 1 for the correct
unit) [5]
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5
Learners sketch a graph of temperature
against time.
D
100
Temperature
/ °C
0
B
Chapter 10
E
Getting started
C
A
Time / min
6
7
8
Energy is being absorbed by molecules during
this time, which causes the molecules to
move more quickly thus increasing their
kinetic energy.
There are two horizontal sections in the
graph. At these points the ice/water are
changing state. Energy is still being provided
but is being used to break the bonds between
molecules so that the ice can melt into
water and the water can change into vapour
that leaves the liquid. During this time the
temperature remains constant.
The temperature of the water might not be
consistent throughout.
Answers to exam-style questions
1
a
b
c
d
Practical investigation 10.1:
Thermal expansion of solids
Beaker [1], tripod [1], heat source /
Bunsen burner [1]
Always stand when heating the water to
avoid scalds; clamp the thermometer so it
doesn’t topple the beaker; take care when
handling the apparatus after use [1 for
each valid consideration, total of 2
marks available]
i
Suitable scale required [1]; axes
labelled including units [1]; correct
1
plot to _​​  2 ​​ square [2]; neatness of plot
and line of best fit – are they
all clear? [1]
ii As the temperature increases, the
mass of sugar dissolved also increases
[1]; data used to support this. [1]
As the temperature of the water increases,
the net kinetic energy of the water
molecules also increases. [1] This means
that the water molecules will collide more
frequently with the sugar, causing it to
break up faster, and thus dissolving it
more easily. [1]
Diagram to include tripod, Bunsen burner,
heatproof mat, beaker on top of the gauze.
Thermometer and soda glass with bung should be
inside the beaker. All parts labelled.
Answers to workbook questions
1
The fluid volume appears to decrease.
2
The fluid volume appears to decrease more
than in the thermometer.
3
The fluid volume appears to decrease less than
in the thermometer.
4
The glass surrounding the fluid expands and
so the internal volume of the tube increases,
giving the impression that the fluid has
decreased in volume.
5
The laboratory glass test tube has expanded
less than the soda glass test tube.
6
From the observations, the fluid in the soda
glass tube seems to dip the most initially. The
glass from which this is made expands more,
compared with the glass of the laboratory
glass tube. The expansion can be measured
more accurately by marking the starting
position of the fluid in the capillary tube and
then marking the point to which it drops.
7
The energy supplied to the molecules in the
metal is enough to weaken the bonds between
molecules and increase their separation so the
metal expands quickly. The bonds between the
glass molecules do not weaken as quickly and
so the glass does not expand. This makes the
lid (slightly) larger than the glass rim and so
easier to open.
[Total: 14]
11
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Practical investigation 10.2:
Measuring the specific heat
capacity of aluminium
Practical investigation 10.3:
Surface area and evaporation
Getting started
Rectangle
length × height
Learners will research a method and the different
pieces of equipment for this investigation.
Circle
πr2
Triangle
base × height
Answers to workbook questions
Getting started
Answers to workbook questions
Example method
°C
100
1
Learners complete their tables.
2
Learners calculate the volume of water
evaporated based on their results.
3
The greater the surface area, the greater the
volume of water evaporated.
4
The containers need to be made of the same
material so the same rate of heat transfer
occurs out of the material.
5
Take repeat readings of the volumes and
calculate the average volume of water lost.
90
80
immersion heater
thermometer
70
60
50
40
30
20
10
0
lagging
solid
block
heat resistant mat
Answers to exam-style questions
Final
temperature / °C
Temperature rise,
/ °C
Specific heat capacity
of lead / J/kg/°C
c = _____
​ ​ ∆E ​​ ; P = IV
m∆
Total energy
transferred / J
Headings: two correct [1]; all four [2]
Starting
temperature / °C
i
Tip
20
22.8
23.6
0.8
5
125
30
22.8
24.1
1.3
7.5
115
40
22.8
24.5
1.7
10
118
50
22.8
24.9
2.1
12.5
19
1
Measure the mass of the block.
2
Measure the energy supplied to the block
(from a 50 W heater for a fixed period of time,
say 5 minutes).
3
Record the temperature change.
Questions
1 Learners record data – exemplar data
provided on Cambridge GO
12
a
No. of turns / n
1
2
904 J/kg °C
3
Aluminium. The aluminium will require more
energy to increase its temperature and so
will transfer less energy to the outside of
the building.
4
900 J/kg °C; the experimental value is
slightly higher,
5
Because some of the energy supplied to
the aluminium will have been lost to
the surroundings.
Temperature rises: two correct [1];
all four [2]
iii Total energy transferred: two correct
[1]; all four [2]
See table. 1 mark per correct answer [4]
The mean of learner’s results is
119 J/kg/C. This result is similar to the
accepted value of 128 J/kg/C. The
value for the learners results is
slightly higher. [1]
ii
b
c
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d
This may be due to the learner
incorrectly measuring the mass of the
lead shot, energy being transferred to
the tube as thermal energy, or any other
sensible suggestion. [1]
Lead is poisonous so should be
handled carefully. [1]
[Total: 13]
Practical investigation 11.2:
Investigating absorption
Getting started
Learners should make a prediction founded on
their results from Practical investigation 11.1 with
a legitimate way of working out the best absorber
of thermal energy.
Answers to workbook questions
Chapter 11
1
Learners record their results in the table.
Practical investigation 11.1:
Conductors of thermal energy
2
Black should be the best absorber. Learners
should make reference to their results to
support their conclusion.
Getting started
3
Variables that may not have been controlled:
the amount of petroleum jelly used; the
distance from the heater to each of the pins.
4
Use a syringe to apply the petroleum to make
sure the same amount is used each time.
To control the thickness of screen, use the
same material and screen thickness for each.
Arrange the screens at an equal distance from
the radiant heater.
5
They need to be at a constant distance to
ensure that the intensity of heat landing on
the screen is constant.
6
There could be a thermometer attached to
the back of the screen to measure the
temperature increase.
•
Good thermal insulators: wool, polyester,
silver foil, fibre glass
•
Poor thermal insulators: cotton, newspaper
•
Independent variable: type of material
•
Dependent variable: temperature of the water
•
Control variable: volume of water, size of
beaker; starting temperature of the water
Answers to workbook questions
1
Table for recording data drawn up, such as the
one below.
Time / s
Temperature / °C
0
Practical investigation 11.3:
Thermal energy transfer
by convection
30
60
Learners should systematically record their
results in a table relevant to their method.
2
13
Learners should construct a graph of
temperature against time. Learners should plot
their results one fabric at a time and then fit in
a line of best fit. The final graph should have
four cooling curves, one for each material.
3
Learners identify the material that enabled
water to cool most slowly and suggest a
reason, such as it being a non-metal with
fixed atoms.
4
A non-metal has no free electrons to transfer
thermal energy quickly.
5
The volume of water was kept consistent at
250 ml using a measuring cylinder.
Getting started
Learners should practise using a pair of compasses
to draw a circle with diameter 10 cm.
Answers to workbook questions
1
Without a candle: turns in different directions,
no pattern in movement.
With one candle: turns clockwise at a
constant rate.
With two candles: turns clockwise at a constant
rate, more quickly than with one candle.
2
As the air is heated the particles in it gain
more energy, causing an increase in the
spacing between them. This causes the air to
become less dense. The unheated (cooler) air
contains particles that are more closely packed
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together, meaning this air is more dense. This
pushes the warmer air upwards, which causes
the spiral to rotate.
3
As the temperature increases with a second
candle, the air particles gain more energy and
move faster as a result. As the particles move
more quickly upwards, the collisions of the
particles with the card are increased and so it
turns more frequently.
4
The type of wax in the candle, the size of the
candle, the thickness of the card, the height of
the spiral.
5
Learners suggest how a circle with small
diameter may behave. Suggestion of
moving faster.
Practical investigation 11.4:
Thermal energy transfer
by radiation
Getting started
Learner to provide a prediction for the
investigation, such as: I think that the black one
will absorb more thermal energy because we paint
things black to help heat things, like in an oven (or
a similar sensible suggestion).
Answers to workbook questions
1
Learners record their results in the table.
2
The blackened aluminium leaf absorbs more
thermal energy as there is a bigger increase
in temperature shown by this thermometer.
Learners should make reference to
their prediction.
3
a
b
14
2
The black matt surface is the best
absorber of thermal energy. [1] It has the
greater increase in temperature over the
time period. [1]
Award 1 mark for any valid answer,
for example: allow cans to cool before
repositioning or packing away; allow
heater to cool before moving. [1]
a
b
c
d
e
Various options are available, such as:
distance from the heat source to the cans;
volume of water; material the can is
made from; starting temperature. (Three
required, 1 mark for each) [3]
i
Independent variable: type of lid [1]
ii Dependent variable: temperature
of water [1]
Volume of water [1]; size of beaker [1]
Thermometer; stopwatch [1]
One learner per thermometer as the
timer starts. [1]
Use a thermometer with smaller
divisions. [1]
[Total: 13]
Chapter 12
Practical investigation 12.1:
Measuring the speed of sound
Getting started
Learners should identify that smooth surfaces are
the best reflectors.
Answers to workbook questions
1
The distance from the wall should be about
50 m measured to the nearest cm.
2
Learners draw up a table to complete
the investigation.
Attempt
Yes the results are valid. This is because the
method accurately measures the amount of
thermal energy absorbed by the different
coloured materials. Variables such as the
distance from the radiant heat source and
surface area exposed were kept controlled so
as not to affect the results.
Answers to exam-style questions
1
c
Time taken
for ten claps
/s
Time taken
for one clap
/s
1
2
3
average
3
4
5
Learners calculate the average time taken for
echo time
​​.
one echo, using _________
​​
10
distance from surface × 2
______________________
​​
Evidence of speed =
​​
time taken for one clap
Results should be in the region of 300 m/s.
Yes – The time for ten claps was recorded
to reduce the error in the timing. No – It
was difficult to distinguish the echo and so
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the timings recorded were inaccurate (or
another sensible suggestion that supports
their argument).
6
7
1
Any discrepancy in centimetres in relation
to the distance will be smaller over a large
distance, for example, 20–50 m, than over a
shorter distance so it can be neglected in
this calculation.
When the blocks are being clapped at a
steady rate, it is more accurate to record the
time taken for a larger number of claps. This
is because any inaccuracy in starting and
stopping the stopwatch is much smaller in
relation to a longer time period than a
shorter one.
Practical investigation 12.2:
Sound through different
substances
a
b
A metal sheet or other smooth surface
such as a hardwood screen. [1]
i
Stopwatch precision = 0.01 s [1]
ii
c
distance
800
​​ [1]; ____
​​
Speed = ________
​​
​​ [1];
2.34
time
342 [1]; m/s [1]
Repeat the experiment to achieve multiple
readings [1] and find the average. [1]
[Total: 8]
Chapter 13
Practical investigation 13.1:
Forming a virtual image in a
plane mirror
Getting started
Getting started
Learners should practise drawing rays of light.
Learners should predict that sound will travel
faster in a solid because the particles are
closer together.
Answers to workbook questions
Answers to workbook questions
1
Learners record their observations.
2
The sound travels more directly through the
particles in the fingers as they are closely
packed. When the fingers are out of the ears
the sound then has to travel from the fingers
through the air to the ear. As the particles are
further apart in the air, it takes longer for the
sound to reach the ear.
3
In solids the particles are packed closely
together and allow the vibrations of the sound
wave to transmit easily. In gases the particles
are much further apart, which results in the
sound taking longer to travel through
the medium.
4
In the water, the particles are spaced further
apart than in a solid. Whilst the sound will be
transmitted, it will be muted compared with
the sound produced when not in the water.
5
For example: It was challenging to hear the
sound with the background noise in the class
(or other sensible answer).
6
15
Answers to exam-style questions
For example: Conduct the investigation in a
quiet room (or other sensible answer).
1
Angle of incidence = angle of reflection
2
Dashed lines represent where light appears to
come from, so they are virtual rays.
3
The image is the same distance from the
mirror as the object is.
4
The image is:
• the same size as the object
• the same distance from the mirror
as the object
• upright
• virtual.
5
A multi-slit screen shows a number of rays
and the point where they converge is where
the image would appear. This would not be
possible using a single slit.
Practical investigation 13.2:
Finding the refractive index
of glass
Getting started
Angles: 45°; 62°; 76°; 22°
Answers to workbook questions
1
Learners should record a range of results at 5°
or 10° intervals between 10° and 80°.
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2
Learners calculate the sines of the angles and
record them in the table.
3
Plot a graph of sin r against sin i. The graph
should be a straight-line graph with a gradient
of approximately 1.5.
4
Learners draw the line of best fit.
5
Calculate the gradient of the graph using the
equation provided. Gradient = 1.5
6
Precision of protractor = 1°
7
The points should show a significant
difference from the line of best fit. To ensure
more accurate results, pins could be used
instead of pencilled crosses or the room could
be darkened.
8
If the line of best fit lies in the range of the
additional points, the measurements taken
are accurate. If the line of best fit falls out of
these points, the results can be improved by
using a sharp pencil, ensure the baseline of
the protractor lines up with the angle being
measured. (Only one suggestion required.)
Practical investigation 13.3:
Dispersion of white light
Getting started
Learners research the different types of prism and
predict the order in which the colours are seen.
Answers to workbook questions
1
2
16
As the prism is rotated, the width of the
spectrum of the refracted beam gets smaller
and then larger as the rotation continues.
Learners should sketch and label the colours
in order: red, orange, yellow, green, blue,
indigo, violet.
3
Red, orange, yellow, green, blue, indigo, violet.
4
Violet. The glass slows down the violet light
more than it does the red and so the angle
through which the violet is refracted is greater.
5
View the spectrum in a darkened room; use a
white screen; use a lens to sharpen the image.
6
Interference from the multiple-slit sources
will produce a different pattern to the
basic spectrum.
7
A beam of white light is observed. The
incident light on the second prism changes
speed as it enters the glass block. This causes
the colours of the spectrum to be refracted
by different amounts, dependent on their
wavelengths, back into the original beam of
white light.
Answers to exam-style questions
1
a
b
i
11.6 cm [1]
ii 4 cm [1]
iii 2.9 [1]
Any two from: lens at the same height
as object; work in a darkened room; all
equipment at right angles to the bench;
ruler fixed to the bench. [2]
[Total: 5]
Chapter 14
Practical investigation 14.1:
Waves on a spring
Getting started
Learners are to practise manipulating the spring
for the investigation to produce both longitudinal
and transverse waves.
Answers to workbook questions
1
Learners record their results in the table.
2
Learners should sketch a transverse wave,
labelling the amplitude.
3
As the speed of the wave is increased the
frequency also increases. The wavelength
might also shorten.
4
Learners should sketch a longitudinal wave,
labelling a compression and a rarefaction.
5
Difficulty: timing the wavefront.
Solution: record, using video and stop frame
for exact time. Or Difficulty: maintaining a
fixed end. Solution: fix to a wall rather than
use another person.
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Practical investigation 14.2:
Investigating the properties
of waves
Getting started
Reflection
Refraction
Diffraction
Angle of
incidence
= angle of
reflection.
No change in
the speed of
the wave.
Wave speed
changes if it
goes into a
more dense
or less dense
medium.
More
diffraction will
occur when
the size of the
gap is equal
to or smaller
than the
wavelength of
the wave.
Answers to workbook questions
1
Learners sketch the reflection of a wavefront
from the boundary, using straight lines to
represent the waveform.
2
The wavelength and the speed
remain constant.
3
The angle of the incoming wave front is equal
to the angle of the reflected wave front.
4
5
6
The shallow water boundary causes the speed
of the wave to decrease. This slowing of the
wave causes the wavefront to bend.
The wave speed decreases as it enters the more
shallow water. The frequency of the wave
remains constant so the wavelength must
also decrease.
Learners draw a diagram of the wave front
before and after it hits the boundary in
the water.
7
Learners draw a diagram of waves passing
through a large gap and a small gap. They
describe the wave pattern, speed and
wavelength after the wave passes through the
gap. See exemplar results on Cambridge GO.
8 Waves are generated by a beam attached to a
motor. The motor oscillates the beam, disrupting
the surface of the water, producing waves.
9 As the wavefront travels into shallower water
the wave slows down, and consequently
changes its direction.
10 The closer the gap in size to the wavelength of
the wave, the greater the diffraction that occurs.
11 The wavelength of light is much smaller than
the wavelength of the water waves. This means
that a much smaller gap in the order of 10−7 m
would need to be used in order to see the
diffraction of the light.
Answers to exam-style questions
1
a
b
c
Transverse wave [1]
Any four from: place bar in the water; set
motor running; measure the size of the
gap; record observations; repeat for
different sizes of gap. [4]
i
barrier
Wavelength remains the same [1];
small diffraction [1]
ii
larger gap
boundary
Wavelength remains the same [1];
large diffraction [1]
17
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iii
d
The closer the gap to the size of
the wavelength [1]; the greater the
diffraction observed. [1]
Any one from: observe in a darkened
room; ensure the bar is submerged in the
water; ensure the frequency of the waves
is low. [1]
b
c
[Total: 12]
Chapter 15
Practical investigation 15.1:
Investigating infrared waves
Getting started
Learners select a number of materials from those
on offer and categorise those that will reflect,
absorb or emit thermal energy.
Answers to workbook questions
1
Learners draw a table for their results.
Material
2
Intensity / W/m2
1
2
3
3
Chapter 16
Practical investigation 16.1:
A magnetic circus
Getting started
Learners should research magnetic materials and
then predict which materials in station 2 would be
magnetic. Examples: fridge door magnetic strip,
fire doors, door locks, earrings, earphones.
Answers to workbook questions
1
The north pole of a bar magnet will attract
the south pole of another magnet. The
magnetic field lines run from the north pole to
the south, which causes the opposing ends to
move towards one another. When like poles
are placed opposite one another the force felt
from the field lines causes a repulsion.
2
The field lines run in a circular pattern on the
outside of the bar magnet, running from one
pole to the other. The iron filings cluster at the
poles, suggesting these are the strongest points
of the magnet.
3
Learners comment on the results of their
investigation at station 2 and their prediction.
4
The magnetic materials were those that
were attracted by the magnet. These
materials included nickel, iron and the steel
ball bearings.
5
Use a piece of card with a magnet placed
underneath. You could also use plotting
compasses instead.
6
For the materials identified as possibly
magnetic, the opposite side of the magnet
should be used to see if the material still
attracts. If it is a magnet it will be repelled by
the test magnet.
Average
Aluminium foil blocked the greatest amount
of radiation. For example, this can be seen
in the results as the reading on the infrared
thermometer dropped to 8 W/m2.
Control
Variable
All the same thickness
where possible –
one layer
Thickness of
material
Same distance each time
Distance from
transmitter
Same size squares
each time
Positioning of
material
Answers to exam-style questions
1
18
a
iIndependent variable: type of
sunscreen [1]; dependent variable:
amount of fluorescence [1]
ii Any two from: the distance of the
plastic from the UV light; the volume
of sunscreen, size of plastic; same
UV light; same volume of
fluorescent matter. [2]
The clear plastic is transparent and will
not block any of the UV light. [1]
Ensure all variables that might affect
the results are controlled and repeat the
experiment to see if the results are
the same. [1]
[Total: 6]
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Practical investigation 16.2:
Exploring magnetic fields
Answers to workbook questions
Station 1
1 Learners draw up a table and record their results.
Getting started
Type of core
The coloured end of the compass represents north.
Answers to workbook questions
1
Learners sketch the
results for opposite
poles facing: N–S.
N
1
S
2
attraction
2
Learners sketch the
results for same poles
facing: N–N, S–S.
N
N
repulsion
3
4
5
The field lines from the north pole of one
magnet connect to the south pole of the other
magnet. The outer field lines still curve but the
inner ones are closely packed together. Field
lines around each magnet still connect from
north to south.
The field lines are closest together near the
poles so the field is strongest here. Iron filings
can be used to display the magnetic fields.
Practical investigation 16.3:
Investigating electromagnets
19
Number of coils; type
of core
Dependent (the one
you measure)
Number of steel
paperclips
Control (the one(s)
you will need to keep
the same)
Current through the
coil; type of core;
number of coils
Average
Number of paperclips
1
2
3
Average
40
60
80
100
4
As the number of turns on the coil of wire
was increased, the number of paperclips
collected by the electromagnet also increased.
For example, when there were 20 turns fewer
paperclips were collected compared to when
there were 80 turns. The core and current were
kept constant so as not to affect the results.
Stations 1 and 2
5 The potential difference was kept at the same
value throughout the experiment to ensure
that the current within the circuit remained
constant. The number of turns on the coil was
kept at 40 so that this did not affect the result.
6
A steel core would not demagnetise.
Altering the core would affect the strength of
the magnet.
7
Any reasonable suggestion such as: loaded one
paper clip at a time; made sure no paperclips
were linked; only added the paperclips in
a chain.
Getting started
Independent (the one
you choose)
3
20
The field lines
for three magnets
will look
like this.
Iron filings or steel pins could be used.
2
The core made from soft iron was the most
effective in the electromagnet. The soft iron
core picked up more paperclips compared
with just one paperclip when using steel. The
wooden core did not magnetise as it failed to
pick up any paperclips. The number of coils
and the current were kept constant so as not
to when using the results.
Station 2
3
Number of
turns
neutral point
6
Number of paperclips
picked up
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Answers to exam-style questions
1
a
b
c
d
e
f
Increase the number of turns on the coil
or use a soft iron core. [1]
The iron nail [1]; as it can become
magnetised. [1]
Plastic is not a magnetic material. [1]
The number of turns on the coil. [1]
i
9 [1]
ii Any sensible suggestion: miscounted
paperclips; there might have been a
break in the circuit. [1]
As the current through the wire increases
the strength of the electromagnet
also increases. [1]
When the current was 0.2 A the
electromagnet could hold four paperclips
but as the current increased to 1.0 A the
number of paperclips increased to 36. [1]
[Total: 9]
2
Station 3
1 Learners record their observations in the table.
Rod combination
Observations
polythene and acrylic
attract
polythene and polythene
repel
acrylic and acrylic
repel
2
As the two rods are brought together they move
towards one another – they attract. This suggests
that the two rods have opposite charges.
3
When two rods of the same material are
brought close together they move away from
one another – they repel. This suggests that
they have the same charge.
Station 2
1 As the balloon is brought over the salt and
pencil shavings it attracts them. As the pencil
shavings are lighter they stick to the balloon
more quickly.
20
uncharged balloons
lie side by side
charged balloons
balloons separate
dampened balloons
balloons almost
return to rest
position
3
The water conducts electrons and so conducts
the static charge away so that the balloons are
no longer charged.
4
Like charges repel; the unlike charges attract.
5
Reduced handling of items that have been
charged. Earth yourself by touching a
conductor; remove rubber-soled shoes.
6
Learners to use ideas about not discharging
themselves or accidentally discharging the
objects, etc. Any sensible suggestions should
be accepted here.
Answers to workbook questions
Station 1
1 Learners record their observations in the table.
Observations
Both of the balloons obtain the same charge
because they are made of the same material
and so they repel one another.
Getting started
Learners will practise handling the rods and
charging them up through friction.
Balloon condition
2
Chapter 17
Practical investigation 17.1:
Investigating static electricity
Both the salt and the pencil shavings have
an opposite charge to the balloon and so are
attracted to it. The charge in the shavings
and salt is induced due to the charge on the
balloon. The pencil shavings, being lighter, are
easier to lift.
Practical investigation 17.2:
Production and detection of
electrostatic charges
Getting started
Learners predict which material will be
electrostatically charged, such as paper and
pencil shavings and concrete wall. This is because
a balloon can stick to a wall once it has been
rubbed due to charge. Or a piece of paper may
stick to another sheet when they come out of
the photocopier.
Answers to workbook questions
1
Concrete, paper and pencil shavings can all be
charged by induction. This was evidenced by
the balloon becoming attracted towards the
previously uncharged materials.
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2
Once the balloon was charged it was handled
only by means of the string or its tied end.
Answers to exam-style questions
1
a
b
c
d
i
By rubbing the rod against a woollen
cloth, clothes, or by friction. [1]
ii Negative [1]; because opposite
charges attract. [1]
Cotton. [1] It does not conduct electricity
[1]; does not have free electrons / is
an insulator. [1]
No. [1] Water conducts away the charge so
the results would be less evident. [1]
The sphere would move away from
the rod. [1]
[Total: 8]
Getting started
Measurement: Current Device: Ammeter in series
Measurement: Voltage Device: Voltmeter in parallel
Answers to workbook questions
1
Learners should draw up a table for
their results.
Resistor number
V/V
I/A
1
2
3
4
Chapter 18
2
Learners calculate the resistances of
their resistors.
3
Getting started
Support: Yes, they are similar. All resistors
have to meet industry standards so must have
a resistance similar to its coding.
Learners discuss reasons why a circuit may be
incomplete and test each of the components.
Examples could be: a break in the circuit; a broken
cell; rust between connections; damage in the wires.
Against: No, they differ significantly. This
might be due to errors in the measuring
devices or resistance between contacts in the
circuit causing inaccurate measurements.
Practical investigation 18.1:
Investigating current
Answers to workbook questions
1
Learners fill in their results table for
series circuits.
2
Learners fill in their results table for
parallel circuits.
3
The current in a series circuit is the same
throughout the circuit.
4
In a parallel circuit the current in the branches
is smaller than the current that is pushed out
of the cell.
5
No. Current is not used up, it remains the
same around a series circuit and the total
current leaving and returning to the cell
remains the same in a parallel circuit.
6
An ammeter. There is no parallax error so
the result is more accurate. A digital ammeter
reads to a greater number of decimal places so
is more sensitive or precise.
7 The switch means that the circuit is off until
turned on, which can reduce the heating
effects of the current on the components.
21
Practical investigation 18.2:
Determining the resistance
4
Precision of ammeter = 0.01 A; precision of
voltmeter = 0.01 V
Practical investigation 18.3:
Investigating current
in components
Getting started
Learners trial the experiment to find a good range
for their results.
Answers to workbook questions
1
Learners draw up tables to record their results.
Potential difference,
p.d. / V
2
Current,
I/A
A graph of current against potential difference
should be drawn. It should be a straight-line
graph through the origin with a gradient
approximating to 100 Ω.
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3
4
5
6
ii
The current–potential difference relationship
is directly proportional. This means that,
when the results are plotted, a straight-line
graph through the origin is obtained.
The resistance of the learner’s resistor will be
1
less. This is because the gradient represents __
​​   ​​
R
An ohmic conductor is a component that
follows Ohm’s law. This means the current
is directly proportional to the potential
difference across it.
iii
2
b
Maintain the resistor’s temperature when
repeating readings (or other sensible answer).
c
Answers to exam-style questions
1
a
a
i
ii
b
A, V, Ω all correct. [1]
1 mark for each correct answer. [4]
V/V
I/A
R/Ω
2.00
0.080
25
1.40
0.034
41
2.00
0.024
83
1.20
0.012
100
Place the resistor on a heatproof mat to
prevent damage to the surface; turn off
the power pack when not in use to reduce
effects of heating. [1]
Correct circuit symbols [1]; correct
positioning of components [1]; straight
lines for wires, drawn with a ruler. [1]
i
Suitable scale required [1]; axes
labelled including units [1]; correct plot
1
to ​​ _2 ​​ square, [2]; neatness of plot and
line of best fit – are they all clear? [1]
c
d
Triangulation method demonstrated
[1]; 24 [1]; Ω [1]
Yes, the learner is correct.[1] It is a
straight line graph that goes through
the origin. [1]
[Total: 19]
Correct circuit symbols [1]; correct
positioning of components [1]; straight
lines for wires, drawn with a ruler. [1]
Read off the thermometer at eye level [1],
stir the water in the water bath to
ensure the temperature is the same
throughout. [1]
i
Voltage = current × resistance [1]
ii V = I × R [1]; 6 = 10 ×10–3 × R [1];
R = 600 [1]; Ω [1]
[Total: 10]
Chapter 19
Practical investigation 19.1:
Light-dependent resistors
Getting started
Learners should try different materials to block
out the light to see which will be most effective.
Answers to workbook questions
1
Learners record their results in the table, see
exemplar results on Cambridge GO.
2
Learners should plot a graph of resistance
against distance.
0.5
Resistance
/Ω
I/A
0.4
0.3
0.2
Distance / m
0.1
0
22
0
2.00
4.00
6.00 8.00
V/V
10.00 12.00
3
As the light intensity decreases the resistance
increases; learners should make reference to
their results to support this.
4
No. As the light intensity decreases, the
resistance will increase and so the current will
drop. This means that the circuit will not work.
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5
Any viable suggestion such as wrapping black
paper around the lamp and LDR or blocking
out the light in some way.
6
A light detector attached to a data logger
could have been used at the set distances to
measure the light intensity.
Practical investigation 19.2:
Thermistors
Getting started
Learners should jot down some notes on particles
and recognise that, as the temperature increases,
the ions in the metal will have increased energy
and so vibrate more.
use; the thermistor should be fully submersed
in the water; water is stirred to ensure the
temperature reading is correct throughout the
water; read the thermometer at eye level to
reduce parallax error; readings are repeated so
that an average can be taken to reduce error.
Practical investigation 19.3:
Investigating resistors in series
and in parallel
Getting started
Learners practise setting up basic series and
parallel circuits so that they are able to get them
working without help.
Dependent variable: resistance
Answers to workbook questions
Independent variable: temperature
1
Learners record their results in the tables.
Answers to workbook questions
2
Learners draw a circuit diagram for the
second circuit.
1
Learners draw up a table, and record
their results.
Temperature
V
Potential Current Resistance
difference
/A
/Ω
/V
A
2
Learners plot a graph of resistance
against temperature.
Resistance
/Ω
3
Learners calculate the average values for p.d.
and current for both circuits and record them
in the tables.
4
Learners should calculate and record the
resistance in both circuits using the formula
V
R = __
​​   ​​
I
The total resistance in the parallel circuit is
less than the resistance in the series circuit.
Learners should refer to their results. For
example, ‘This can be seen in the experimental
results. The resistance in the parallel circuit is
3 Ω whereas in the series circuit it is 30 Ω’.
Temperature / °C
23
3
For an NTC thermistor, as the temperature
increases the resistance decreases. Learners
should refer to their own results, for example,
‘This is illustrated in the experimental results.
When the temperature is 40 °C the resistance is
250 Ω but drops to 100 Ω when the temperature
increases to 70 °C’.
4
Any two of: ensure readings on the
thermometer are taken from eye level; check
for non-zero error on the ohmmeter before
5
6
There is no parallax error so the result is
more accurate. The digital ammeter reads to
a greater number of decimal places so is more
sensitive or precise.
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Practical investigation 19.4:
Investigating fuses
Chapter 20
Answers to workbook questions
1
Learners record their results in the table.
2
Learners should state the current at which the
fuse blows.
3
The fuse did not blow because the current
flowing through the circuit was lower than the
rating value and so did not heat the fuse wire
up enough to cause it to melt.
4
Yes. The fuse wire melted at a current similar
to the rating on the fuse wire.
5
The current in the circuit that causes the
fuse to blow might be related to a p.d. that
is between a whole-number interval. The
variable resistor allows for more sensitive
readings to be taken.
6
There is no parallax error so the result is
more accurate. The digital ammeter reads to
a greater number of decimal places so is more
sensitive or precise.
Practical investigation 20.1:
Making a relay circuit
Getting started
De-magnetise them by heating or dropping and
check that they do not attract anything metallic.
Answers to workbook questions
1
The lamp in the 12 V circuit is turned off.
2
The lamp in the 12 V circuit is turned on.
3
When the 1.5 V circuit is turned on, the C-core
becomes magnetised and attracts the steel
strip. As the steel strip moves downwards
the contact wires touch, completing the 12 V
circuit, causing the lamp to turn on.
4
This protects the user as the voltage in the
1.5 V circuit will be at a much safer level than
in the 12 V circuit.
5
The strip must be made from steel, iron,
cobalt or nickel as it needs to be attracted to
the C-core to make a contact and complete the
12 V circuit.
6
Increase the current in the smaller circuit or
increase the number of turns on the coil.
Answers to exam-style questions
d
e
24
Total resistance in
the circuit, R / Ω
Appearance of
the lamp
c
I/A
b
Voltmeter in parallel to all components or
across the cell. [1]
See table, two correct [1], all three [2]
V/V
a
Circuit
1
1
1.49
0.50
3.0
bright
2
1.48
0.22
6.7
dim
i
V
R = __
​​   ​​ [1]
I
ii See table, 3.0 [1]; 4.5 [1]
See table: circuit 1 – bright [1];
circuit 2 – dim [1]
If the learner added another resistor in
parallel to the other resistors in each of
the circuits this would reduce the effective
resistance of both circuits. [1] Placing a
resistor in parallel to another makes it
easier for the current to flow reducing the
total resistance in the circuit. [1]
[Total: 10]
Practical investigation 20.2:
The motor effect
Getting started
Learners should draw the field lines between the
magnets. Field lines should run from north to
south in straight lines between the poles and in
curved lines above and below the poles for the
pairs of north and south poles.
For the pair of north poles, the field lines go
towards each other and then through 90 degrees
upwards and downwards so that they are parallel
near an imaginary line that is halfway between
the poles.The angle between the wire and the field
would be 90°.
Answers to workbook questions
1
The wire moved (and might be forced out of
the magnetic field, depending on the polarity
of their connection to the cell).
2
The wire moved in the opposite direction.
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3
It will cause the wire to move in the
opposite direction.
4
Fibreglass is an insulator and so will not
conduct electricity, so the wire would
not move.
5
a
b
c
All three correct [2]; two correct [1]
i
As the circuit is turned on the rod will
move [1] outwards [1].
ii The rod will move [1] in the
opposite direction. [1]
i
Increase the current [1]; increase the
strength of the magnets. [1]
ii The copper rod is a conductor [1]
[Total: 9]
Chapter 21
Practical investigation 21.1:
Electromagnetic induction
in a coil
Getting started
Readings: 6 μA, 14 μA, 12 μA, 2 μA
Answers to workbook questions
1
25
When the magnet is pushed inside the coil of
wire the arm on the galvanometer deflects.
Learners should provide a reading.
2
When removing the magnet, the arm of the
galvanometer will deflect in the opposite
direction. Learners should provide a reading.
3
When the magnet remains in the coil the arm
of the galvanometer should not deflect.
4
The arm of the galvanometer deflects further
each way.
5
The arm of the galvanometer deflects further
and faster each way.
6
The greater the number of turns, the greater
the induced e.m.f., so the greater the
current induced.
7
Dependent variable: induced e.m.f. or current;
independent variable: number of turns of
the coil.
9
The size of the magnetic field; keep the
magnets the same throughout. The speed at
which the magnet is inserted into the coil;
insert into the coil at a consistent speed.
Increase the current in the wire or increase the
strength of the magnets.
Answers to exam-style questions
1
8
The faster the movement of the magnet within
the coil, the greater the induced e.m.f. and
thus the greater the induced current.
10 It has a greater sensitivity than an ammeter
so will detect smaller currents and can also
indicate the direction of current flow.
Practical investigation 21.2:
Investigating transformers
Getting started
Learners correctly identify primary coil, secondary
coil and soft iron core (yoke).
Answers to workbook questions
1
The lamp is dimly lit when there are 20 turns
on the primary coil.
2
Learners should make a prediction and give
reasoning to support their prediction.
3
The brightness of the lamp increases as the
number of turns increases.
4
Learners state whether their observation
supports their prediction.
5
Prediction related to an increase in brightness.
Reason: adding the yoke increases the magnetic
flux in the transformer and so will increase the
induced e.m.f. in the secondary coil.
6
Learners should state with reason if their
observation supports their prediction.
7
A step-down transformer. The mains voltage
is 230 V but the bulb has a p.d. of 2.5 V so the
voltage across the secondary is lower than that
across the primary.
8
A voltmeter could be placed across the bulb
to take readings for voltage or an ammeter
placed in the circuit to measure the current.
This can then be compared to what is supplied
to the primary coil.
Answers to exam-style questions
1
a
Independent variable: speed of rotation
[1]; dependent variable: the induced e.m.f.
[1]; control variables: the magnetic field
strength; number of turns on the coil
(both correct [1])
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b
c
One from: keep the magnets the same
each time; maintain a constant number of
coils of wire. [1]
A voltmeter [1]
[Total: 5]
4
2
Chapter 22
He
Practical investigation 22.1:
The structure of the atom
Getting started
•
•
•
Protons – positive charge, atomic mass of 1,
in nucleus
Neutrons – no charge, atomic mass of 1,
in nucleus
Electrons – negative charge, negligible mass,
in orbitals or shells around nucleus
7
3
3
Each different type of bead represents a
different sub-atomic particle. The proton and
neutron beads are collected in the centre of
the plate in the nucleus, while the electron
beads are positioned as orbitals on the outer
edges of the plate.
4
Similarities: there are three different types of
particle (bead); they are arranged similarly.
Differences: there is no free space in this
model. The sizes of the atom and particles,
and their spacing, are not proportionate or
representative of those in the atom.
5
Ideas could include: include orbitals for
electrons; make the model three-dimensional;
create free space in the model.
6
There is free space between the planets; the
planets orbit a central core.
Answers to workbook questions
1
Sketch the atoms you have created.
2
Adapt your models to illustrate an isotope
of each of the elements​​147​N​,​126​C​, ​42​He​and ​73​Li​.
Sketch these isotopes.
14
7
Li
N
Practical investigation 22.2:
The alpha scattering experiment
Getting started
Learners make predictions about how the rolling
balls might behave when the bottles are in the
different configurations described.
Answers to workbook questions
12
6
26
C
1
The table tennis balls represent the alpha
particles. Each drinks bottle represents
an atom and the curvature of the bottle
represents the nuclear force of the atom.
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2
The ball moves collides with the bottle and
rolls back in the same direction.
3
The ball deflects away from the bottle as it
collides with the side of the bottle.
4
The more off-axis the impact, the smaller the
deflection of the table tennis ball from the
centre of the bottle.
5
The ball deflects fully because the curvature is
at its greatest at this point.
6
The size of the nucleus is small in comparison
to the size of the atom so the -particles
would rarely collide head-on with the nucleus.
7
Similarities in the model: a large number of
balls would pass through the model; balls will
deflect with a greater angle the closer to the
centre of the bottle they are fired.
2
Learners draw a graph of a decay curve, based
on their results.
Remaining
dice
Number of rolls
3
Learners should draw the curve of best fit on
the graph.
4
Half-life is four spins, based on model data.
Answers to exam-style questions
5
1 a i
7
ii 14
iii 7
iv 7
b iThe nucleus is positively charged as it
has repelled a positive particle. Law
of electrostatics, like charges repel.
ii 1) The nucleus is very small in size
2) the majority of the atom is
empty space.
The half-life results are similar. This is
representative of radioisotopes of the same
element. Each time the spinners are spun there
is the same probability that a spinner will land
on a 6. This will give rise to the same
decay pattern.
6
Six spinners, based on the model data.
7
If the sample size is increased to 50 the halflife will remain the same.
8
The process by which the spinners land on
the 6 is random. However, over a period of
time, a pattern emerges and a curve is
produced similar to what you would see in
radioactive decay.
9
Spinners are being used rather than decaying
nuclei. There are no radioactive emissions; the
spinners do not change once they have rolled.
[Total: 7]
Chapter 23
Practical investigation 23.1:
Radioactive decay model
10 Yes this is an appropriate model. Learners to
suggest a model that may work.
Getting started
Answers to exam-style questions
Demonstration to show the idea of a half-life.
1
a
Answers to workbook questions
1
27
Learners record their results in the table.
Results should range from 25 spinners
remaining to one spinner remaining.
b
164 ÷ 3 [1] = 55 (2 s.f.) [1]
Any two from: artificial sources;
cosmic rays; food and drink; radon;
ground and buildings; medical [2]
Any two from: sources should be kept in
a lead lined box in a metal storage box;
should bear the radioactive symbol on
the box; should be handled with tongs;
learners should stand a safe distance
from the source; do not direct the source
at anyone. [2]
i
ii
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c
d
i
As the thickness of the aluminium
sheet increases, the amount of betadecay passing through decreases [1];
supporting reference from data. [1]
ii Any one from: use same detector;
same distance of source from
the sheet. [1]
She could repeat the investigation and
take an average of the results. [1]
[Total: 10]
Practical investigation 24.1:
Phases of the Moon
28
The shadow cast creates the crescent moon.
4
The new moon is in full shadow so it is unable
to be observed.
5
The distances from the Sun and Earth could
have been to scale. A scale model of the Sun,
Moon and Earth could have been used.
6
The Moon would have been between the
observer and the Sun.
7
a
Day
Chapter 24
•
•
The lamp represents the Sun.
The ball represents the Moon.
1
Learners record their observations in the table.
2
See table
Point from
starting
position
3
Sketch
observation
of the ball
Phase of the
moon
At start
Full moon
​​ _18 ​​ turn
anticlockwise
Waning
gibbous
​​ _14 ​​ turn
anticlockwise
Last quarter
​​ _38 ​​ turn
anticlockwise
Waning
crescent
​​ _12 ​​ way
through cycle
New moon
​​ _58 ​​ turn
anticlockwise
Waxing
crescent
​​ _34 ​​ turn
anticlockwise
First quarter
​​ _78 ​​ turn
anticlockwise
Waxing
gibbous
Back to starting
position
Full moon
Sketch
Phase of the
moon
1
Full moon
7
First quarter
14
New moon
21
Third quarter
28
Full moon
b
The Moon takes approximately 28 days to
orbit the Earth. The radius of the Moon’s
orbit is approximately 3.5 × 108 m
i
ii
2r
V = ​​ ____ ​​
T
2 ×  × 3.5 × 108
_________________
​​     ​​
(28 × 24 × 60 × 60)
[1] for subs; [1] for conversion of time
period
V = 909 m/s [1]
V = 0.91 km/s [1]
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021
CAMBRIDGE IGCSE™ PHYSICS PRACTICAL WORKBOOK ANSWERS
c
• It is elliptical
• It orbits the Sun
• It changes in speed / fater the closer to
the Sun
Answers to exam-style questions
1
a
Length, l / m
Time, T / s
(Time)2, T 2 / s2
0.1
0.63
0.397
0.2
0.89
0.792
0.3
1.10
1.21
0.4
1.26
1.59
0.5
1.41
1.99
0.6
1.55
2.40
0.7
1.67
2.79
Chapter 25
Practical investigation 25.1:
Determining the acceleration
of freefall
Getting started
a
b
c
12.5 m/s
15 m/s
7.5 m/s
b
Answers to workbook questions
1
Learners record their data in the table.
c
d
2
Learners calculate the speed for each height of
card drop using the relevant data and record it
in the final column of the table.
e
3
Learners calculate v2 for each height of card
drop and record it in the table.
4
Learners plot a graph of v2 on the vertical
axis and the height of card drop, h, on the
horizontal axis.
5
Learners should calculate an answer using the
triangulation method in the region of 10 m/s2.
6
They are directly proportional (since the graph
is a straight line through the origin).
7
Learners research values of g on other
planets: Mars 3.7; Jupiter 24.79; Saturn 10.4;
Mercury 3.7.
8
As the size of the planet increases the
acceleration due to freefall increases. This
causes the weight to increase (reverse
argument also true). Learners should use data
to support their argument.
9
Any two from: the timer; human reaction
time; poor alignment with gate; card released
from incorrect height.
See table. All correct [2]; minimum of half
correct [1]
f
Graph should have labelled axes with
units [1]; all plotted correctly [1]
Line of best fit should be straight [1]
Gradient should show triangulation
method [1]; value should be
approximately 4.0 [1]
These readings may include an error. [1]
Repeating the measurements and taking
an average will reduce the effect of
the error. [1]
The learner should record the time taken
for ten oscillations (or sensible number
suggested). [1] This can then be divided
by 10 to find the time period for
one oscillation. [1]
[Total: 11]
10 Learners make suggestions relevant to errors
listed, for example always use the same person
releasing the ball, film the fall of the ball, use
a marker as a starting point, use a marker
on the ball and the ruler so they align before
release (or other sensible suggestion).
29
Cambridge IGCSE™ Physics Practical Workbook – Nightingale © Cambridge University Press 2021