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Mock Exam Paper 1
Mock-CE
PHY
PAPER 1
Name
Class
Class number
Teacher's Use Only
Section A Question No.
Marks
1
2
3
4
5
6
7
8
9
Section A Total
Section B Question No.
Marks
10
11
12
13
Section B Total
MOCK EXAMINATION
PHYSICS PAPER 1
Question-Answer Book
(1¾ hours)
This paper must be answered in English
1 Write your Name, Class and Class number in the spaces
provided on the this cover.
2 This paper consists of TWO sections, Section A and Section
B. Section A carries 54 marks and Section B carries 36
marks.
3 Answer ALL questions in each section. Write your answers
in the spaces provided in this Question-Answer Book.
Supplementary answer sheets will be supplied on request.
Write your Name on each sheet and fasten them with string
inside this book.
4 Some questions contains parts marked with an asterisk (*).
In answering these parts, candidates are required to give
paragraph-length answers. In each of these parts, one mark
is allocated to assess candidates' ability in effective
communication.
5 Unless otherwise specified, numerical answers should be
either exact or correct to 3 significant figures.
6 Take g = 10 m s–2
.
7 Unless otherwise specified, all the cells are assumed to have
negligible resistance.
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Useful Formulae in Physics
(a) Relationships between initial velocity u, uniform acceleration a, final velocity v and
displacement travelled s after time t:
v = u + at
2
2
1atuts
asuv 222
(b) Potential energy gained by a body of mass m when raised through a height h is mgh.
(c) Kinetic energy of a body of mass m moving with speed v is 2
2
1mv .
(d) Power = force velocity
(e) Equivalent resistance of two resistors R1 and R2 :
(i) in series = R1 + R2
(ii) in parallel21
21
RR
RR
(f) Power = potential difference current
SECTION A (54 marks)
Answer ALL questions in this section and write your answers in the spaces provided.
Question No. 1 2 3 4 5 6 7 8 9
Marks 4 5 6 6 6 8 5 6 8
1 Figure 1 shows a compact fluorescent lamp.
Figure 1 Figure 2
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Figure 2 is the enlarged image showing the specifications of the lamp:
20 W 220–240 V 50–60 Hz
In Hong Kong, the mains voltage is 220 V.
(a) Find the operating current of the lamp. (2 marks)
(b) Find the operating resistance of the lamp. (2 marks)
2 John produces a wave by flicking an elastic string. He produces 2 complete waveforms
every second. Figure 3 shows the shape of the elastic string at a certain time t.
Figure 3
(a) Is the wave produced transverse or longitudinal? (1 mark)
(b) Find the wavelength and the amplitude of the wave. (2 marks)
(c) In Figure 3, draw the waveform at time t + 0.125 s. (2 marks)
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3 Jane wants to find the focal length of a convex lens. She uses the lens to project the image
of a distant building on a screen. She measures the distance between the lens and the image
and finds it 15 cm.
(a) State a property of the image. (1 mark)
(b) What is the focal length of the lens? (1 mark)
She then uses the lens to form the image of a nearby object on a screen. She puts the object
20 cm from the lens. The object is 10 cm high.
(c) In Figure 4, use a scale of 1 cm to 10 and draw a ray diagram to locate the image.
Hence find the magnification of the image. (4 marks)
Figure 4
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4 A fire breaks out in a building. A resident is waiting for rescue on the 8th floor. The
firemen arrive soon and open a large air cushion below the resident (Figure 5). The
resident (mass 60 kg) jumps down onto the cushion.
Figure 5
(a) If each storey of the building is 3.5 m high, find the speed of the resident at the
moment when he reaches the cushion. The cushion is 3 m thick when inflated.
(2 marks)
(b) After reaching the cushion, the resident slows down and comes to a stop after 0.2
seconds. Calculate the average net force acting on the resident during this period.
(2 marks)
(c) The resident later says that he crawled close to the floor when moving in the
smoke-filled building. Comment on whether he acts correctly. (2 marks)
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5 It is found that passengers taking New YorkHong Kong flight would receive radiation
equivalent to that of three X-ray scans (about 20 Sv for each X-ray scan). The high
radiation of New YorkHong Kong flight is due to the long flight time and also the high
flight altitude.
(a) ‘Sv’ is a unit of radiation dose. What does the dose mean? (2 marks)
(b) What kind of radiation may the passengers receive inside the plane? (1 mark)
(c) State a main source of this background radiation. (1 mark)
(d) A nuclear plant is another source of nuclear radiation. Do you agree with the use of
nuclear energy? Give two reasons to support your position. (2 marks)
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6
Figure 6
In Figure 6, the roller-coaster ‘Dragon’ in Ocean Park of mass 1500 kg is about to travel
down a track from rest at a point A which is 110 m above ground level. Take the potential
energy at ground level as zero.
(a) Find
(i) the potential energy of the cart at point A,
(ii) the speed of the cart at a point B which is 89 m above ground level, assuming
friction is negligible. (4 marks)
(b) The actual speed of the cart at B is less than that in part (a)(ii). Describe the energy
change as the cart moves from A to B. (2 marks)
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6 (c) In Figure 7, complete the following free-body diagram for the cart when it is going
downhill. (2 marks)
Figure 7
7
Figure 8
Figure 8 shows the structure of a loudspeaker. The coil is wound round the S-pole of a
cylindrical magnet. Attached to the cone, the coil is free to move inside the magnet.
(a) The coil is connected to an a.c. power supply. What happens to the cone when the
supply is switched on and a current flows into the coil from A? (1 mark)
*(b) Describe the working principle of the loudspeaker. (4 marks)
cart
weight
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8 Read the following passage about electric light bulbs and answer the questions that follow:
The structure of a light bulb is very simple. At the base, it has two metal contacts,
which connect to the mains circuit. The metal contacts are attached to two stiff metal
wires, which are attached to a thin metal filament. The filament is held in the middle
of the glass bulb. The glass bulb is filled with an inert gas, such as argon.
The filament in a light bulb is made of a long, thin wire of tungsten metal. The
filament for a 60-W bulb can be as long as 2 m, but it is made into a coil of less than
3 cm long. Tungsten has the highest melting point (3422 C) among all metals.
When the bulb is connected to a power supply, an electric current flows through the
filament. The current heats up the filament. When the filament is hot enough, it gives
out visible light. For tungsten, it emits a large amount of visible light when its
temperature reaches about 2200 °C.
At such an extreme temperature, some tungsten will change into vapour. If the
inside of the bulb is a vacuum, tungsten becomes vapour easily and the filament will
disintegrate in a short time. This greatly reduces the life of the bulb.
Today inert gases such as argon are used to fill the bulbs. The gas makes
vaporization of tungsten much slower. Besides, it does not react with tungsten. This
extends the life of the bulbs.
Source: HowStuffWorks http://science.howstuffworks.com/light-bulb2.htm
(a) You are given two light bulbs, A and B. Bulb A has a thinner filament than bulb B.
Write down the relationship between the resistance and the length and cross-sectional
area of the filament. Hence state which bulb has a lower resistance. The filaments are
of the same material and length. (2 marks)
(b) State an advantage of using tungsten over other metals for making the bulb filament.
(1 mark)
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8 (c) But tungsten normally catches fire at the temperature mentioned in the passage.
Explain why this does not happen inside the bulb. (1 mark)
(d) Describe the energy change in a light bulb, hence explain whether the light bulb is an
efficient source of light. (2 marks)
9 Many Chinese ‘dim sums’ are cooked by steam. In order to keep the food warm, a dim
sum cart is used as shown in Figure 9. There is a heater inside the cart to boil water and the
food steamers are made of bamboo.
Figure 9
(a) List one advantage of cooking by steam. (1 mark)
(b) State the process by which energy is transferred from the heater to the food steamers
at the top. (1 mark)
food steamer
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9 (c) A student says that the food inside the steamers at the top is hotter than that at the
bottom. Comment on this statement. (2 marks)
(d) Explain why the food steamer is made of bamboo. (2 marks)
(e) If the power of the heater is 200 W, how much water at 100 C will be boiled away in
each minute?
(Given: Specific latent heat of vaporization of water = 2.26 106 J kg
–1.) (2 marks)
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SECTION B (36 marks)
Answer ALL questions in this section and write your answers in the spaces provided.
Question No. 10 11 12 13
Marks 5 7 9 15
*10 You feel hot and sweat (Figure 10). When you turn on a fan, you will feel cooler than
when the fan is not turned on. Explain why. (5 marks)
Figure 10
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11 Figure 11 shows an induction cooker.
Figure 11
Under the plastic plate of the cooker are some coils. A high-frequency a.c. flows through
the coils. The rapidly changing magnetic field produces a strong eddy current inside metal
pots placed on the plastic plate. The heating effect of the eddy current cooks the food
inside the pot.
(a) Can one use the cooker to cook rice in a clay pot? Explain briefly. (2 marks)
(b) The power of the above induction cooker is 1500 W. A family uses it to make hot pot
and switches it on for 4 hours. If each unit of electricity costs $0.9, what is the cost of
electricity for using the cooker? (2 marks)
(c) What happens to the heating effect of the cooker if
(i) the frequency of the a.c. is lowered;
(ii) coils with more turns are used? (2 marks)
(d) The induction cooker makes use of eddy current. But in some situations eddy current
should be avoided. State one such situation. (1 mark)
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12 Figure 12 shows two loudspeakers, A and B, connected to the same signal generator. The
generator produces sound waves at 500 Hz. Initially, only A is switched on. The speed of
sound is 340 m s1
.
Figure 12
(a) Figure 13 shows the displacement-time graph of an air molecule at P.
Figure 13
Figure 14
(i) Indicate the values for t1 and t2.
(ii) In Figure 14, draw the displacement-distance graph of the sound wave along AP
at t = 0.002 s.
(5 marks)
(b) Then B is also switched on. One can hear a series of loud and faint sounds when
walking across in front of the loudspeakers. What happens to the loudness of sound
heard at P? Explain briefly. (3 marks)
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(c) In daily life, one cannot hear similar changes in loudness when walking across in
front of the loudspeakers of a hi-fi system playing a song. Explain why. (1 mark)
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13
Figure 15
Figure 15 shows the set-up of a data-logging experiment on a horizontal table to
investigate impacts. Two trolleys, A and B, collide with each other and their motions are
recorded by motion sensors. The mass of trolley A and trolley B is 0.69 kg and 1.38 kg
respectively. The velocity-time graphs captured by motion sensors for trolleys A and B are
shown in Figures 16 and 17 respectively.
Figure 16 Velocity-time graph for trolley A
Figure 17 Velocity-time graph for trolley B
*(a) Describe the motions of trolleys A and B before and after the collision. (5 marks)
For the shaded region, Mean value of y = -0.59
For the shaded region, Mean value of y = 0
For the shaded region, Mean value of y = 0.54
For the shaded region, Mean value of y = 0.22
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(b) In Figures 16 and 17, what is the physical meaning of the area bounded by the curve
and the horizontal axis? (1 mark)
(c) (i) Do the results support the conservation of momentum? Show your calculations.
(3 marks)
(ii) Give one source of error and one suggestion for improvement. (2 marks)
(d) Calculate the total kinetic energy of the trolleys before and after the collision. Hence
explain briefly if the collision is elastic.
(4 marks)
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END OF PAPER
