Download S4 Final Examination (05-06)Paper I

S4 2005-2006 FINAL EXAMINATION – PHY I
S4
Full marks : 90 marks
SHATIN TSUNG TSIN SECONDARY SCHOOL
2005-06 FINAL EXAMINATION
PHYSICS I
Student : _____________________________(
)
Date : 20/6/2006
Time allowed : 1 3/4 hour
Instructions :
1. This paper consists of Two sections, Section A and Section B. Section A carries 54 marks and Section B
carries 36 marks.
2. Answer ALL questions in each section. Write your answers in the spaces provided. Supplementary answer
sheets and graph papers will be supplied on request.
3. 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 communications.
4. Take g = 10 ms-2
Section A (54 marks)
Answer ALL questions in this section.
Question No.
1
2
Marks
4
6
1.
3
6
4
8
5
7
6
8
7
8
8
7
RADAR (Radio Detecting And Ranging) is a useful device in air traffic control. In Figure 1, an aircraft is
flying near a radar station. A pulse of electromagnetic wave with a speed of 3 x 10 8 m s-1 and a frequency of
1.2 x 10 9 Hz is emitted from the radar station towards the aircraft.
10 µs
Figure 1
Figure 2
(a) Find the wavelength of the electromagnetic wave.
(2 marks)
(b) The electromagnetic wave pulse which is emitted is reflected by the aircraft back to the radar station.
The emitted and reflected pulses are displayed on the screen of a CRO as shown in Figure 2. The
time-base setting of the CRO is 10 µs per division (1 µs=10-6s). Estimate the distance between the radar
station and the aircraft.
(2 marks)
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S4 2005-2006 FINAL EXAMINATION – PHY I
2.
P.2
RADAR, as mention in Question 1, is a useful device to detect aircraft. However, the air forces of many
countries try to build aircraft that can hide away from their enemies. Read the following passage about a
stealth bomber (See Figure 3)
Stealth Bomber
There are some special features in the design of the stealth bomber to make it invisible
to enemy sensors. The aircraft needs to blend in with the background visually and its
engine needs to be very quiet. Furthermore, it needs to hide from enemy radar and
infrared sensors. Defending against radar detecting, the surface of the stealth bomber is
particularly good at absorbing radio wave. More importantly, the large flat areas on the
top and bottom of the aircraft reflect most incoming radio waves away from the radar
station in the same manner as plane mirrors usually reflect light rays away from light
sources. In regard to infrared sensors typically picking up on hot engine exhaust, all of
the exhausts in a stealth bomber pass through cooling vents before flowing out of the
plane. With the designs mentioned above, a stealth bomber has the ability to fly almost
undetected through enemy airspace.
Figure 3
Source : http://science.howstuffworks.com/stealth-bomber3.htm
(a) (i)
In Figure 4, draw a ray to show how a wave from the radar is reflected at the bottom of the
stealth bomber.
(1 mark)
Figure 4
(ii)
If the stealth bomber flies horizontally to a particular position around the radar, it can be
detected by the radar. Mark this position with a symbol X in Figure 4.
(1 mark)
(b) All of the exhausts in a stealth bomber pass through cooling vents before flowing out of the plane. Explain
how this can help the stealth bomber to hide away from enemy detection.
(2 marks)
(c) Apart from the designs which help prevent the stealth bomber being detected by radar and infrared sensors,
state two other essential features which are important in building the stealth bomber so that it can hide
away from enemy detection.
(2 marks)
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S4 2005-2006 FINAL EXAMINATION – PHY I
3.
P.3
A student releases a book of mass 0.154 kg from rest under a motion sensor as shown in Figure 5. The
velocity-time graph is recorded in Figure 6.
Figure 5
(a)
Figure 6
From the graph in Figure 6, estimate the distance travelled by the book.
(b)
Find the loss in potential energy of the book during the journey in (a)
(c)
From the graph in Figure 6, find the maximum kinetic energy of the book.
(d)
Account for the difference in the values obtained in (b) and (c)
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(2 marks)
(1 mark)
(2 marks)
(1 mark)
S4 2005-2006 FINAL EXAMINATION – PHY I
P.4
4.
Figure 7
Figure 7 shows a conveyor belt in a factory. A parcel of mass 10 kg is placed at position P when the belt remains at
rest. The workman controls the belt such that the parcel undergoes a motion described in Table 1. The parcel and
the conveyor belt move together without slipping during the entire motion.
Position of the parcel
P -> Q
Q -> R
R -> S
Motion
Uniform acceleration
Uniform velocity
Uniform deceleration to rest
Table 1
Data given
PQ= 5 m and time required = 2s
---------------
(a) Consider the motion when the parcel travels from P to Q.
(i) Draw a free-body diagram to show all forces acting on the parcel in the space provided below. Name
the forces.
(2 marks)
(ii) Find the net force acting on the parcel.
(3 marks)
(b) In Figure 8, sketch a graph to show the variation of the frictional force exerted by the conveyor belt on the
parcel.
(3 marks)
Force
P
Q
R
S
Figure 8
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Position of the parcel
S4 2005-2006 FINAL EXAMINATION – PHY I
5.
P.5
Figures 9a and 9b shows the same plastic lens L mounted on the rear window of the same car. The driver can
view his friend David, and the surroundings at the back of the car through either the rear window or lens L as
shown in Figure 9b.
Lens
David
Figure 9a
Lens
Figure 9b
(a) What kind of lens is L ? Explain your answer.
(2 marks)
(b) Suppose that David in Figure 9b stands at 60 cm from lens L of focal length 30 cm. In Figure 10,
David is plotted as AB. Draw a ray diagram to show how the image of David is formed by lens L.
Use a horizontal scale of 1 cm to 10 cm.
(4 marks)
A
B
Figure 10
(c) State one advantage of using lens L.
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(1 mark)
S4 2005-2006 FINAL EXAMINATION – PHY I
6.
P.6
The information in Table 2 was taken out from an energy label of a water heater
Rated Capacity
24.1 litres
Heating time
24.3 minutes
(15oC 65oC)
Table 2
Given: mass of 1 litre of water = 1 kg,
Specific heat capacity of water = 4200 J kg-1 oC-1,
Specific latent heat of ice = 2.26 x 106 J kg-1
(a) The heating element of a water heater is usually installed on the lower position of the water tank.
Suggest one reason for this design.
(1 mark)
(b) Using the information in Table 2, estimate the energy required to heat a full tank of water from
(2 marks)
15oC to 65 oC,
(c) In using the water heater to take a bath, ice of 0oC is mixed with the hot water to lower down the
water temperature to 38oC. Assuming that the hot water is 65oC, how much ice is required to mix
with the hot water of 5 kg ?
(4 marks)
(d) In practice, less amount of ice is required, give one reason for this.
(1 mark)
7. *(a) A light ray emerges from a glass block of refractive index 1.5 to water of refractive index 1.33 as shown
in Figure 11. Describe and explain how the path of the refracted light ray changes when the angle of
(6 marks)
incidence gradually changes from 0o to 70o.
Glass, n =1.5
Water, n =1.33
Figure 11
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S4 2005-2006 FINAL EXAMINATION – PHY I
P.7
(c) Optical fibres are widely used in telephone communication. The voice signals are transmitted in the form
of light through optical fibres. Figure 12 shows a light ray travelling towards an optical fibre. In Figure 12,
sketch the subsequent path of the ray.
(2 marks)
Figure 12
8.
Figure 13 shows the 2 ifc (International Financial Centre) in Central. The building is about
420 m high and lifts take 2 minutes to travel from the ground floor to the top of the building.
Each lift can take 20 persons of 75 kg each at most. The mass of each lift is 1800 kg. The
highest speed of each lift is 9ms-1 .
a)
What is the useful power output required by each lift in operation?
(3 marks)
Figure 13
b)
If each lift takes 10 s to reach its highest speed, what are the two tensions required in the lift cable in
travelling upwards and downwards?
(4 marks)
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S4 2005-2006 FINAL EXAMINATION – PHY I
P.8
Section B (36 marks)
Answer ALL questions in this section and write your answers in the spaces provided in this Question-Answer
Book.
Question No.
9
10
11
Marks
12
12
12
9.
Read the following descriptions about a ‘crash cushion system’ and answer the questions that follow.
Figure 14
Figure 15
Figure 14 and Figure 15 show a crash cushion system installed at some junctions on highways. The system
consists of a number of identical cushion boxes, containing sand or water, lined up and fixed on the road
surface. During a crash, the boxes will burst one after another when the car runs through them. The boxes
will act as a series of cushions and offer protection to the passengers.
Figure 16
In a pilot test on the cushion boxes, a car of mass 1600 kg travelling at a speed of 27 ms-1 runs through the
boxes on a road (see Figure 16). The speed v of the car after running through all the boxes is recorded. The
test is repeated by varying the number of boxes N installed in the system. The table below shows the results
obtained.
N
1
2
3
4
v/m s-1
252.
22.8
21.1
18.2
Table 3
(a) Assume that the deceleration of the car remains unchanged in the test.
(i)
Using the data in Table 3, plot a graph of v2 against N in Figure 17, with v2 ranging from 0 to
1000m2s-2 and N from 0 to 10.
Figure 17
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S4 2005-2006 FINAL EXAMINATION – PHY I
P.9
Hence or otherwise, estimate
(1)
(2)
(ii)
(b)
the average resistive force exerted by the cushion boxes on the car during the collision (given
that the thickness of each cushion box is 1 m),
(7 marks)
the minimum number of cushion boxes required in order to stop the car in the test.
(1 mark)
If the test is repeated with a heavier car travelling at an initial speed lower than 27 m s-1, sketch a
graph of v2 against N in Figure 17 that you would expect to obtain. Use a dotted line to sketch the
graph. Assume that the average resistive force acting on the car remains unchanged throughout all the
tests.
(2 marks)
Explain why it is undesirable to replace the cushion boxes with concrete blocks.
(2 marks)
10. Dehumidifiers (see Figure 18) are used to lower the humidity of air. Wet air flows into Part A of the
dehumidifier and dry air flows out from Part B of the dehumidifier as shown in Figure 19. A liquid called the
refrigerant circulates through the coiled tube. The refrigerant absorbs heat from the wet air and evaporates
inside the coiled tube in Part A. The vapour of the refrigerant is then pumped to the coiled tube in Part B
where it is compressed and condenses into a liquid. The liquid refrigerant then passes back to the coiled tube
in Part A and the process is repeated.
Figure 18
Figure 19
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S4 2005-2006 FINAL EXAMINATION – PHY I
P.10
(a) In terms of molecular motion, explain why the temperature of the refrigerant drops when it evaporates
inside the coiled tube in Part A.
(2 marks)
(b) Explain two reasons why the coiled tube in Part A is designed in a coiled shape.
(2 marks)
(c) In the coiled tube in Part B, the vapour of the refrigerant is compressed and condenses into liquid. State the
change of the average potential energy of the refrigerant molecules during this process of changing state.
(1 mark)
(d) When the dehumidifier is in operation, the coiled tube in Part B gives out heat. State and explain two
designs that could prevent the dehumidifier from overheating.
(2 marks)
(e) The dehumidifier is turned on for a few hours in a closed room. Water vapour in the incoming wet air
condenses and 15 kg of water is collected in the water tank (see Figure 19)
(i) Estimate the total energy released by the water vapour. The specific latent heat of vaporization of
water is 2.2 x 10 6 J kg-1.
(2 marks)
(ii) Using the data and the formula in Table 4, estimate the increase in temperature of the air in the room,
assuming that all the energy released in Part B is used to raise the temperature of the air inside the
room.
(3 marks)
Volume of the air in the room = 400 m3
Density of the air = 1.3 kg m-3
Specific heat capacity of the air = 1030 J kg-1 oC-1
Mass = density x volume
Table 4
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S4 2005-2006 FINAL EXAMINATION – PHY I
P.11
11. A student would like to investigate the interference of micorwave in his school laboratory. His set-up consists
of a microwave emitter and one microwave receiver as shown in Figure 20. The signal received is then
displayed in a CRO. The following is a set up of his experiment.
P
S1
Microwave
emitter
Q
R
Receiver
S2
Steel plate with
two slits of 3 cm
opening
CRO
Figure 20
a)
What is the purpose of using a steel plate with two slits of 3 cm opening in this experiment?(2 marks)
He placed the reciever at positions P and Q and R and the results in the CRO are recorded in Table 5.
Position
Distance from S1
Distance from S2
Signal recorded
P
36 cm
42 cm
Maximum
Q
33 cm
36 cm
Maximum
R
30 cm
30 cm
Maximum
Table 5
b)
c)
Draw in Figure 20 how the microwaves travelled.
From the Table 5, find the longest possible wavelength of the microwave.
(3 marks)
(3 marks)
d)
What is the least possible frequency of the microwave?
(2 marks)
e)
His classmate said that the whole set-up can still be used to investigate the interference of visible light.
Comment on his classmate’s statement.
(2 marks)
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S4 2005-2006 FINAL EXAMINATION – PHY I
Answer :
HKCE Paper 2006
1. HKCE 2006 Q1
2.
3.
4.
5.
HKCE 2006 Q2
HKCE 2006 Q3
HKCE 2006 Q4
HKCE 2006 Q5
6. HKCE 2006 Q6
7. a) The emerging light ray will bend away from the normal. As the angle of incidence increases, the
angle of refraction also increases. When the angle of incidence is about 60o (the critical angle), the
angle of incidence is now 90o. If the angle of incidence further increases, total internal reflection
occurs and there will be no refraction at all.
b) HKCE 2005 10
8. a)
b)
Useful power output = useful / time interval
P = mgh / t = (1800 + 20 x 75)(10)(420)/(2x60) = 115500 W or 116 kW
a = v/t= 9/10 =0.9 ms-2
Upwards : F = ma
T-3300x10 = 3300 x 0.9
T =35970N or 36.0 kN
Downwards:
3300 x 10 – T = 3300 x 0.9
T = 30030 M or 30 kN
9)
HKCE 2006 Qn 9
10) HKCE 2006 Qn 10
11) a) The steel plate is ensure that the two microwaves coming out of S1 and S2 are oringinate from the
same source, which is the microwave emitter, thus the two sources are coherent.
c)The longest wavelenght is the HCF of the tow possible wavelenght.
From P, path difference is 6 cm = nλ
From Q, path difference is 3 cm = nλ
From R, path difference is 0cm. = nλ
So λ is 3 cm
d) The least frequency:
Since v = f λ
3 x 10 8 = f x 0.03
f = 1x1010 Hz
e) No, the set-up cannot be used with visible light as the wavelength of visible light is too small and
is between 400 nm to 700 nm, no diffraction occurs after passing through the two slits. Interference cannot
occur.
- End of Paper -
S4 2005-2006 FINAL EXAMINATION – PHY I
- End of Paper -