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St. Joseph’s Anglo-Chinese School
Second Term Examination 2006/2007
Form 4 Physics Paper 1
Name: __________________
Class No.: _______________
(Time allowed: 1 ¾ hours)
This paper must be answered in English.
1.
Write your name and class number in the spaces provided on 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.
4.
Some questions contain 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 ms-2.
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
1
s  ut  at 2
2
v 2  u 2  2as
(b) Potential energy gained by a body of mass m when raised through a height h is mgh.
1
(c) Kinetic energy of a body of mass m moving with speed v is mv 2 .
2
(d) Power = force x velocity
Section A (54 marks)
Answer ALL questions in this section and write your answers in the spaces provided.
1
Question No.
1
2
3
4
5
6
7
8
Marks
9
8
11
6
5
4
7
4
An object is placed in front of lens L. Figure 1 shows a light ray from the object is refracted by L.
Figure 1
(a)
What type of lens is L?
(1 mark)
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(b)
Complete the ray diagram in Figure 1 to show how an image is formed.
(2 marks)
(c)
State the nature of the image.
(2 marks)
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(d)
By adding a suitable light ray in Figure 1, find the focal length of the lens.
(2 marks)
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(e)
Find magnification of the image.
(2 marks)
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2.
A signal of 2 kHz is fed into two loudspeakers S1 and S2. as shown in Figure 2.
S1
A
P
S2
B
Figure 2
(a) Describe and explain what would be heard as one walks along AB.
(2 marks)
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(b) What is the separation of the loudspeakers if they are about 2 wavelengths apart? (Speed of
sound in air = 340 m s–1)
(2
marks)
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(c) It is known that S1P = 34 cm and S2P = 59.5 cm. What would be heard at P? Explain your
answer.
(4 marks)
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3
Figure 3 shows a racing car Nissan 350Z. It can reach 100 km h1 from rest in 6 s.
Figure 3
In a journey, it accelerates at this rate for 10 s, then travels at uniform speed for 500 m and
decelerates uniformly to rest in 20 s.
(a) (i) Show that the maximum speed of the car in the journey is 46.3 ms-1.
(ii) Find the time that the car takes to travel the 500 m in the middle of the journey, and the
total time for the whole journey.
(7 marks)
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(b)
Sketch a graph to show how the speed of the car varies with time for the whole journey.
(4 marks)
2
4
A naughty boy, standing on the roof of a building, aims at a girl waiting near the building and
releases a bag of water. The girl notices the falling bag when it is 5 m above her head. The
building is 20m tall and the girl is 1.5 m tall.
(a) What is the velocity of the bag when the girl sees it?
(2 marks)
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(b)
Assume the reaction time (i.e. the time lapse between seeing the bag and starting to run
away) of the girl is 0.3 s. Explain whether the bag will hit her head.
(4 marks)
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5
A student of mass 60 kg is sitting on a chair.
(a) Find the weight of the student.
(1 mark)
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(b)
Find the normal reaction acting on the student from the chair.
(1 mark)
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(c)
Do the weight of the student and the normal reaction acting on him form an
reaction-and-reaction pair? Explain briefly.
(3 marks)
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6
Macau Tower is the 10th tallest free-standing tower in the world. Its height is 338 m and its main
observation level is 223 m above ground. A lift installed in the tower can travel at an average
speed of 4.96 m s1.
(a) The lift transports a load of 1800 kg from the ground to the main observation level. Find the
work done on the load by the lift.
(2 marks)
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(b)
What is the average useful power of the lift?
(2 marks)
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Figure 4
The figure above shows part of the route of a roller-coaster in an amusement park. A cart full of
passengers with total mass 1200 kg runs down from rest at the starting point H to the terminal
platform. H is 30 m above the terminal platform. The track provides an average frictional force of
300 N throughout the journey.
(a) The cart travels a distance of 150 m to reach the highest point A of the vertical loop, which is
20 m above the terminal platform.
(i)
In moving from H to A, calculate
(1) the loss in potential energy,
(2) the work done against friction, and
(3) the gain in kinetic energy of the cart.
(ii) Find the speed of the cart at A.
(7 marks)
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4
8
Read the following passage about timing devices and answer the questions that follow.
Timing devices
In the past, the rotation of the Earth about its axis defines the day, which is a basic unit
of time. The ever-changing position of the Sun (sunrise and sunset) acted as a simple
and convenient clock. The revolution of the Earth about the Sun defines the length of a
year.
However, the Earth's rotation and revolution are not as regular as were once assumed.
As a result, the research and development of more uniform and accurate timing device
have never stopped. Right now, the atomic (cesium) clock is the most accurate timing
device in the world. A cesium atom kept in a constant state will always precisely and
stably make 9192 631 770 complete cycles of vibration per second. By counting each
vibration, the clock is more precise than the rotation of the Earth. Cesium clocks are
accurate to two nanoseconds (2  109 s) a day or one second every 1400 000 years.
Much of modern life depends on precise timekeeping. For example, safe and accurate
navigation of ships and aeroplanes requires timely and correct location of their
positions; this relies on the punctual arrival of positioning signals from four Global
Positioning System (GPS) satellites. Extremely accurate timekeeping is required, since
the signals (microwaves) travel at the speed of light (3  108 m s1), any tiny error in the
time signal could result in incomplete information.
(a) Give two reasons why cesium clock is much more accurate than the Earth's rotation in
measuring time.
(2 marks)
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(b) Explain briefly why accurate timekeeping is important in GPS.
(2 marks)
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Section B (36 marks)
Answer ALL questions in this section and write your answers in the spaces provided.
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Question No.
9
10
11
12
Marks
6
13
12
5
Figure 5 shows the displacement-distance graph of a traveling transverse wave at t = 0 s. The
wave is traveling to the right. The frequency of the wave is 5 Hz.
displacement / cm
4
P
S
2
0
distance / cm
Q
10
20
30
40
-2
-4
R
Figure 5
(a) Find
(i) the amplitude and
(ii) the wavelength of the wave?
(b) Describe the motion of particles P and S at t = 0.
(c) Sketch the displacement – time graph of particle Q from t = 0 to 0.4 s.
(1 mark)
(1 mark)
(2 marks)
(2 marks)
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10.
Figure 6
Figure 7
Two metal balls P and Q are suspended by light inextensible strings. Ball P is pulled to a point A
which is at a height h above its initial position B and is then released. (See Figure 6.) After
colliding at B, the two balls move away in opposite directions. (See Figure 7.)
(a)
Draw a diagram to show all the forces acting on P when it swings from A to B. Label the
forces.
(2 marks)
(b)
Describe the energy changes in the balls, from the moment P is released until the balls
swing up to their maximum heights after the collision
(4 marks)
(c)
The mass of P is 0.3 kg and its speed immediately before the collision is found to be 1m s-1.
(i)
Find h.
(2 marks)
(ii)
Consider the following set of data:
P
0.3
Q
0.75
velocity before collision / ms-1
1.0
(towards the right)
0
Velocity after collision / m s-1
0.5
(towards the left)
0.6
(towards the right)
Mass/ kg
(1)
Show that the above set of data obeys the law of conservation of momentum.
(2)
Explain why the above set of data is impossible.
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(5 marks)
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8
11
A truck of mass 5000 kg travels with a constant velocity of 20 m s1 to the left on a horizontal
ground. It collides with a thick wall fixed to the ground (earth) as shown in the following figure.
The truck is brought to stop rapidly in 0.2 s.
20 m s1
Figure 8
(a) By the law of conservation of momentum, the wall should acquire a velocity in the collision.
i* (i)
Explain why it seems to be at rest after the collision.
(ii) Find the average force of impact on the driver of mass 70 kg.
(3 marks)
(2 marks)
(iii) If a cushion is placed in front of the wall, what will be the effect on the impact force on
the driver? Explain briefly.
(2 marks)
(b) Suppose the wall is replaced with a car of mass 1000 kg and after the collision the truck
sticks with the car and both slide together forwards.
(i)
Find the velocity of the vehicles immediately after the impact.
(2 marks)
(ii) Suppose the friction of the road is 25 000 N, what will be the distance travelled by the
two vehicles after the collision?
(3 marks)
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10
12
A hi-fi loudspeaker unit usually has two or more speaker cones of different sizes. One speaker
cone is for producing low-pitch sounds and the others for sounds of higher pitches. The sound
waves produced by the speaker cones will bend around the rim of the cones and spread into the
room.
rim of speaker
cone
Figure 9
(a) Name the wave phenomenon described above.
*(b) Which speaker cone is more suitable for high-pitch sounds? Explain briefly.
(1 mark)
(4 marks)
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--- End of Paper ---
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