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CCC Hoh Fuk Tong College
Second Term Examination, 2003 – 2004
Physics I
Secondary:
Four
Time allowed: 1¾ hour (8:15 - 10:00 a.m.)
Date: 18/06/2004
Full Mark: 90
1.
This paper consists of TWO sections, Section A and Section B. Section A carries
54 marks and Section B carries 36 marks.
2.
Some questions contain parts marked with an asterisk (*). In answering these
parts, you are required to give paragraph-length answers. In each of these parts,
one mark is allocated to assess the ability in effective communication.
3.
Unless otherwise specified, numerical answers should be either exact or correct to
3 significant figures.
4.
Take: velocity of light in vacuum = 3  108 m s-1
acceleration due to gravity = 10 m s-2
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SECTION A (54 marks)
Question No.
1
2
3
4
5
6
7
8
9
Marks
5
6
6
5
6
11
6
4
5
1.
2.
Remote controls are widely used nowadays to control domestic appliances.
(a)
What kind of electromagnetic waves is used for remote controls? Could
we determine the colour of it by our eyes?
(2)
(b)
If the wavelength of the signal is 10-4 m, what is its frequency?
(2)
(c)
State one other application of this kind of electromagnetic wave.
(1)
In an experiment, a ray of light travels across an air-glass boundary as shown.
air
glass
The following table shows the results obtained.
angle of incidence i
15o
30o
45o
angle of refraction r
9o
18o
26o
(a)
Copy and complete the table below.
(2)
angle of incidence i
15o
30o
45o
angle of refraction r
9o
18o
26o
sin i
sin r
sin i
sin r
(b)
sin i
Find the mean value of sin r . What is its physical meaning?
(2)
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(c)
3.
4.
5.
Calculate the angle of refraction if the angle of incidence is 75o.
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(2)
A small coin is placed in front of a convex lens of focal length 20 cm, such that
the size of the image is equal to the size of the object.
(a)
Determine the object distance and image distance.
(2)
(b)
Draw a ray diagram to show how the image is formed.
(2)
(c)
State the nature (real/virtual and erect/inverted) of the image.
(2)
The figure below shows two cars in a racing course. Car A is moving at a uniform
speed of 20 m s–1 and car B is initially at rest.
(a)
In order for car B to overtake car A before car A passes the finishing line,
car B accelerates at an acceleration of 5 m s–2. Find the time taken for car
B to reach the finishing line.
(2)
(b)
Find the time taken for car A to reach the finishing line.
(2)
(c)
Which car will pass the finishing line first?
(1)
Star Ferry travels nearly along a straight line between Tsim Sha Tsui and Central.
It starts at Tsim Sha Tsui and takes 2 minutes to accelerate to a velocity of 0.15
km min1. It then travels at a constant speed for 6 minutes. Finally, the ferry
slows down uniformly and stops in 2 minutes.
(a)
Sketch a graph showing the velocity-time graph of the ferry.
(4)
(b)
From (a), find out the displacement travelled by the ferry.
(2)
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7
Car A stopped suddenly on the road. At that instant, another car B was 30 m
behind and travelling on the same road at a uniform velocity of 15 m s-1.
B
I.
A
II.
B
A
30 m
At the instant the driver of car B saw car A being stopped, he applied the brake as
soon as possible. The following is the velocity-time graph of car B.
7.
(a)
What is the reaction time of the driver of car B?
(1)
(b)
Find the deceleration of car B from t = 0.6 s to 4 s.
(2)
(c)
Find the stopping distance of car B. Will car B crash into car A?
(4)
*(d)
For safety, cars are installed with seat belts. Explain why.
(4)
Read the following news about a traffic accident on Tuen Mun Road and answer
the questions that follow.
A traffic accident occurred on Tuen Mun Road in Tsuen Wan this morning (10
July, 2003) in which 21 persons were killed and 20 others were injured.
At about 6:30 am, a double-decker travelling along Tuen Mun Road collided
with a container truck. After the collision, the bus crashed against the road
barrier and came to rest on the edge of the road momentarily. The bus then fell
onto a slope 30 metres below and slid another 20 metres before stopping.
There are few survivors in this terrible accident, including a nine-year-old girl
who walked away from the accident without any injury and a taxi driver who
claimed he survived because he fell onto other passengers’ bodies.
(a)
Estimate the speed of the bus just before hitting the slope. Assume that the
bus fell from rest. Ignore the length of the bus and air resistance in your
calculation.
(2)
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8.
(b)
Describe the passengers’ feeling of their body weight as the bus fell
vertically down to the slope.
(2)
(c)
Briefly explain why falling onto other passengers’ bodies could save the
taxi driver.
(2)
Two connected boxes are at rest on a smooth surface. John uses 100 N to pull
them to the right.
30 kg
9.
7
20 kg
100 N
(a)
Find the accelerations of the boxes.
(2)
(b)
Find the tension in the string connecting the boxes.
(2)
A block of mass 2 kg is placed on a rough surface and is pulled by a force F as
shown.
2 kg
F
(a)
The block starts to move at constant speed when F is increased to 5 N.
What is the friction between the block and the surface?
(1)
(b)
Find the acceleration of the block when F is increased to 8 N.
(c)
The force is suddenly removed when the block is moving. Find the
subsequent acceleration pf the block.
(2)
(2)
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SECTION B (36 marks)
Question No.
10
11
12
13
Marks
8
11
9
8
10.
A ball is thrown vertically upwards at A with an initial speed of 10 m s-1 from the
top of a building. It takes 6 seconds to reach the ground. Take the upward
direction as positive.
B
A
H
C
11.
(a)
What is its speed and acceleration of the ball at B?
(2)
(b)
What is the distance AB?
(2)
(c)
What is the height of the building?
(2)
(d)
What is the speed of the ball on striking the ground at C?
(2)
A hot-air balloon is tied to the ground by two ropes to stop it from taking off. The
weight of the balloon is 7650 N and the upward force is 8000 N.
upward force = 8000 N
weight = 7650 N
rope
rope
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The ropes are cut and the balloon starts to move upwards.
12.
13.
(a)
Find the tension in each string before cutting the ropes.
(2)
(b)
Calculate the initial acceleration of the balloon.
(3)
*(c)
Explain how the acceleration of the balloon changes during the first ten
seconds of its flight.
(4)
(d)
When the balloon is still accelerating, the balloonist throws some bags of
sand over the side. Explain how this affects the acceleration of the
balloon.
(2)
A man of mass 50 kg carries out an experiment in a lift. Inside the lift, he steps
on a weighing scale graduated in newtons.
(a)
Draw a free-body diagram to show all forces on the man. Label the forces
drawn.
(2)
(b)
If the scale reads 550 N. Find all possible accelerations of the lift. (4)
(c)
If the scale reads 500 N, the lift must be at rest. Is it correct? Explain
briefly.
(3)
The figure shows a man pulling an ice block of 100 kg.
(a)
If the friction between the ground and the ice is 150 N, find the force
needed to pull the ice with a uniform speed.
(2)
(b)
Suggest a method to reduce the magnitude of the applied force.
*(c)
“Although it is hard to pull the ice initially, but it is easier to pull it at a
latter time.”
Comment on this statement and explain briefly.
(4)
*** END OF PAPER ***
(2)