B
Name
OXFORD UNIVERSITY PRESS
Class
NEW SENIOR SECONDARY
Class number
PHYSICS AT WORK
(SECOND EDITION)
Teacher's
MOCK EXAMINATION (Set 2) Use Only
PHYSICS PAPER 1 Question No. Marks
Section B: Question-Answer Book B 1 /8
This paper must be answered in English 2 /5
3 /7
INSTRUCTIONS FOR SECTION B
(1) After the announcement of the start of the examination, 4 /9
you should first insert your information in the spaces
5 /7
provided on Page 1.
6 /9
(2) Refer to the general instructions on the cover of the
Question Paper for Section A. 7 / 11
(3) Answer ALL questions.
8 /6
(4) Write your answers in the spaces provided in this
Question-Answer Book. Do not write in the margins. 9 /8
Answers written in the margins will not be marked. 10 /6
(5) Graph paper and supplementary answer sheets will be
11 /8
provided on request. Insert the information required, mark
the question number box, and fasten them with string Total / 84
INSIDE this Question-Answer Book.
(6) No extra time will be given for inserting your information
or filling in the question number boxes after the ‘Time is
up’ announcement.
New Senior Secondary Physics at Work (Second Edition)
Mock Exam (Set 2) Paper 1B 1
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Section B: Answer ALL questions. Parts marked with * involve knowledge of the extension
component. Write your answers in the spaces provided.
1 Susan cooks two sets of identical food at the same rate in two pots. The pots are of the
same size and shape, but one is made of aluminium and the other is made of clay. The
table below shows some data about aluminium and clay.
Specific heat capacity Ability to conduct heat
/ J kg–1 C–1 / relative unit
Aluminium 897 205
Clay 1381 0.2
(a) After the food boils, Susan takes the two pots away from the stove. Which pot can
Answers written in the margins will not be marked.
better keep the food hot after they are taken away from the stove? Explain your
answer briefly. (3 marks)
(b) Which pot of food requires a shorter time to reach boiling? Why? (3 marks)
(c) If both pots are at 60 C, which of them feels hotter when touched? Explain your
answer briefly. (2 marks)
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*2 Amy has a bowl with a lid as shown in Figure 2.1. The lid is a rigid and unbendable disk
which can seal the bowl tightly. The weight of the lid is 0.3 N.
lid
a layer of oil
soup
Figure 2.1
The air temperature and pressure in the room is 15 C and 100 kPa respectively. Amy
pours some warm soup into the bowl and then covers the bowl with the lid. The mouth of
the bowl has a cross-sectional area of 100 cm2. A layer of oil floating on the soup prevents
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evaporation and keeps the air inside the bowl dry.
(a) The temperature of the soup and air inside the bowl is 30 °C when the lid is closed.
After a certain time, the temperature inside the bowl drops to the room temperature.
Estimate the air pressure inside the bowl. (2 marks)
(b) Amy pulls the handle of the lid and finds it difficult to open. Estimate the minimum
force required to lift the lid. (2 marks)
(c) Suggest ONE method how she can lift the lid more easily. (1 mark)
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3 A car of mass 1500 kg accelerates from rest to 80 km h–1.
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Figure 3.1 (photo credit: Benis Arapovic | Dreamstime.com)
(a) Name the force provided to the car by the ground that accelerates the car. (1 mark)
(b) The force described in (a) has a maximum value of 10 000 N. At this maximum
value, find the distance travelled by the car if the driver reduces its speed from
80 km h–1 to zero. (3 marks)
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*(c) The car now enters a circular path of radius 50 m. The driver keeps the car
travelling at 80 km h–1. Find the centripetal force required to keep the car on the
circular path. Will the car skid on the road? (3 marks)
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4 An object of mass 0.1 kg is put on the platform of a machine (Fig 4.1). When the machine
is triggered, it pushes the platform upwards very quickly (Fig 4.2). The object leaves the
platform after the platform reaches its highest position (Fig 4.3). The maximum height
that the object reaches is 20 cm above the highest position of the platform. The
displacement of the platform is 5 cm in the whole process. Its mass is negligible when
compared with that of the object.
object
platform
machine
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Figure 4.1 Figure 4.2 Figure 4.3
(a) Find the object’s speed at the instant it leaves the platform. (2 marks)
(b) The object falls back on the platform. Find its time of flight in air. (2 marks)
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(c) Figure 4.4 shows the v-t graph of the object, taking upwards as positive.
0 t
slope = 4g
Figure 4.4
Find the time taken for the platform to move from its initial position to its highest
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position. (2 marks)
(d) Find the average power output of the machine. (3 marks)
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5 (a) You are given an inextensible light string, a mass and a protractor. Describe a
method to measure the acceleration of a vehicle on a horizontal road using the
given apparatuses. State any assumptions made. (5 marks)
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(b) A man is standing on a balance inside a lift. He finds that he is heavier than normal
when the lift is accelerating upwards. Briefly explain why. (2 marks)
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6 An object O is placed in front of a lens L as shown in Figure 6.1. A light ray from O is
refracted by the lens.
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Figure 6.1
(a) What kind of lens is L? (1 mark)
(b) Locate the image I of O in Figure 6.1. (2 marks)
(c) State TWO properties of the image. (2 marks)
(d) Locate the principal focus F of L in Figure 6.1. What is the focal length of the lens?
(3 marks)
(e) Give ONE application of lens L. (1 mark)
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7 (a) (i) A series of sound waves travel from water to air as shown in Figure 7.1.
air
water
sound waves
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Figure 7.1
Draw the refracted sound waves in the figure. (2 marks)
(ii) A light ray travels out of the water into air with the same angle of incidence
as shown in Figure 7.2.
air
water
light ray
Figure 7.2
Draw the refracted light ray in the figure. (1 mark)
(iii) Explain the difference between the travelling directions of the refracted
waves/ray in (i) and (ii). (1 mark)
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(b) The frequencies of a beam of light and a beam of sound are respectively
6 × 1014 Hz and 600 Hz.
(i) Find the wavelengths of the two waves in air.
Given: The speed of sound in air is 340 m s–1. (2 marks)
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(ii) State TWO ways to increase the degree of diffraction when a train of
straight waves passes through a small gap. (2 mark)
(iii) Describe what happens to the light and sound waves if they pass through a
gap of width 0.2 m. Explain the difference. (3 marks)
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8 Read the following article about ‘Faraday cage’ and answer the questions that follow.
A Faraday cage is simply a cage made of a perfect conductor (Fig 8.1). When a
Faraday cage is placed in an electric field, its free electrons will redistribute themselves
to cancel all electric field inside the cage. Therefore, an external electric field cannot
reach the interior of a Faraday cage. This makes the Faraday cage a good shield against
electric fields.
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Figure 8.1 (photo credit: Wikipedia/Antoine Taveneaux)
When lightning strikes a car, as long as the passengers inside are not in contact with
the metallic parts of the car, the car chamber acts like a Faraday cage and protects the
passengers from electric shock (but that does not mean they are completely safe as the
car could catch fire easily).
The effect could be bad sometimes. A Faraday cage can shield varying electric fields,
such as mobile phone signals. This is the reason why our mobile phones usually suffer
a poor signal reception inside a lift with steel walls.
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(a) Figure 8.2 shows the cross-section of a Faraday’s cage in a uniform electric field.
Draw in the figure to show how the electric field is cancelled inside the cage.
(2 marks)
Faraday cage
Figure 8.2
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(b) Sometimes, mobile phone signals are not completely cut off inside a lift. Suggest
TWO reasons for this. (2 marks)
(c) Explain why the car may catch fire when lightning strikes the car. (2 marks)
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9 John designs an electroscope as shown in Figure 9.1. The electroscope consists of two
identical small metal spheres hanging freely by two conducting wires, which are
connected to a metal probe. The mass of each sphere is 0.1 g and the masses of the metal
wires are negligible. The length of each wire is 5 cm, which is much larger than the
diameters of the spheres. Initially, the charge stored inside the electroscope is zero.
insulating
block
metal probe
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Diagram NOT drawn to scale
Figure 9.1
(a) John touches a charged object momentarily with the metal probe. A total charge of
Q flows into the electroscope through the probe. He assumes that all the charges are
stored in the metal spheres.
(i) How much charge does each sphere store? (1 mark)
(ii) Let θ be the angle between the two wires. Express the distance between the
two spheres in terms of θ. (1 mark)
(iii) State and explain ONE source of error in the above calculations. (2 marks)
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(b) Suggest how John can clear the charges inside the electroscope. (1 mark)
(c) John has a galvanometer (as shown in Figure 9.2 below) and some connecting
wires.
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Figure 9.2
Describe how he can check the sign of the charges stored inside the electroscope.
(3 marks)
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*10 A metal rod initially slides on a smooth horizontal surface at 1.5 m s–1. A uniform
magnetic field of 0.025 T points downwards perpendicularly to the surface. Figure 10.1
shows the top view of the set-up.
30 B = 0.025 T
X
–1
1.5 m s
P
top view
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Figure 10.1
(a) Find the direction and magnitude of the magnetic force acting on electron X as
shown in the figure. (3 marks)
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(b) Hence state whether an electron at P or Q has a higher electric potential energy
after a while. (1 mark)
(c) Iris says that the sliding speed of the rod is continuously decreasing. Is she correct?
Explain your answer. (2 marks)
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11 Strontium-89 ( 89
38 Sr) is injected to a patient’s body for bone cancer treatment. It decays to
form yttrium (Y) by emitting a beta particle. The half-life of strontium-89 is 50 days.
(a) Write a nuclear equation for the decay of strontium-89 into yttrium. (1 mark)
(b) Radium-223 is also used for bone cancer treatment and has a half-life of 11.4 days.
Suggest an advantage of using radium-223 over strontium-89. (1 mark)
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(c) The activity of a sample of Strontium-89 is 148 MBq. How much time has passed
when its activity drops to 1 MBq? (2 marks)
*(d) Given: mass of a strontium nucleus = 88.907 451 u
mass of a yttrium nucleus = 88.905 848 u
mass of an electron = 0.000 549 u
(i) Why is the total mass different before and after the decay? (1 mark)
(ii) Estimate the kinetic energy (in joule) of the emitted β particle. State the
assumption made in the calculation. (3 marks)
END OF PAPER
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Mock Exam (Set 2) Paper 1B 18
© Oxford University Press 2015
