Precious Blood Secondary School
2011/2012 Final Examination
Form 4 Physics Paper 1
Time Allowed: 1 hour 30 mins
Full Marks: 100
Form: 4_____
Name:______________________
Class Number: _______________
GENERAL INSTRUCTIONS
1. There are TWO sections, A and B, in this Paper. Section A consists of multiple-choice questions in this question
book, while Section B contains conventional questions printed separately in Question–Answer Book B. You are
advised to finish Section A in about 25 minutes.
2.
Answers to Section A should be marked on the Multiple-choice Answer Sheet while answers to Section B
should be written in the spaces provided in Question-Answer Book B. The Answer Sheet for Section A and the
Question-Answer Book for Section B must be handed in separately at the end of the examination.
INSTRUCTIONS FOR SECTION A
1.
Read the instructions on the Answer Sheet carefully.
2.
When told to open this book, you should check that all the questions are there. Look for the words ‘END OF
SECTION A’ after the last question.
All questions carry equal marks.
ANSWER ALL QUESTIONS. You should use an HB pencil to mark all your answers on the Answer Sheet.
Wrong marks must be completely erased.
You should mark only ONE answer for each question. If you mark more than one answer, you will receive NO
MARKS for that question.
No marks will be deducted for wrong answer.
3.
4.
5.
6.
1
Section A Multiple Choice (36 marks)
There are 18 Questions. Questions marked with “*” involve knowledge of the extension component. The last page of
this question paper contains a list of data, formulae and relationship which you may find useful.
1. The boiling points of four gases are shown below. When they are cooled down from room temperature, which of
them will condense first?
gas
argon
neon
nitrogen
oxygen
A.
B.
C.
D.
boiling point / °C
−186
−246
−196
−183
2. Which of the following phenomena can be explained by evaporation?
(1) Wet clothes eventually dry under the Sun.
(2) We feel cold when we leave a pool of water.
(3) Mist forms on a can of cold drink.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D.
(1), (2) and (3)
3. Two beakers of water labelled as A and B are at a temperature of 70C initially. Some oil of the same temperature
is added to beaker A. Then the two beakers are put on a bench at room temperature to cool down for a long time.
Which of the following graphs best shows how the temperatures of the liquids vary with time?
A.
B.
temperature / C
temperature / C
70
70
A
B
B
A
0
time / s
0
C.
time / s
D.
temperature / C
temperature / C
70
70
B
B
A
A
0
time / s
0
time / s
4. Which of the following ways can slow down the cooling process of a cup of hot water?
(1) Wrapping the cup in aluminium foil.
(2) Roughening the surface of the cup.
(3) Covering the cup with a lid.
A. (1) only
B. (3) only
C.
(1) and (2) only
D.
(1) and (3) only
*5. The pressure of a fixed mass of an ideal gas is decreased from 500 kPa to 460 kPa while its volume is kept
constant. If the temperature change of the gas is 40°C, what is the final temperature of the gas?
A. 15.0°C
B. 55°C
C. 187°C
D. 227°C
Answer: C
3
*6. A sealed container of volume 1 m is filled with an ideal gas of temperature 22°C and pressure 140 kPa. What is t
2
A.
the number of mole of gas molecules?
3.44×10−21 mol
B. 5.71×10−2 mol
C.
57.1 mol
D.
766 mol
*7. Brownian motion of smoke particles can be observed using a smoke cell under a microscope. Which of the
following account for the path of the motion of the smoke particles?
(1) A smoke particle is much heavier than an air molecule.
(2) Smoke particles are collided by air molecules frequently.
(3) The air molecules move in zigzag paths.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
*8. What of the following conditions is the most favourable for a real gas behaving like an ideal gas?
A. low temperature and low pressure
B low temperature and high pressure
C
high temperature and low pressure
D
high temperature and high pressure
*9. Molecules A, B and C are travelling at speeds of vA, vB and vC respectively. What is the r.m.s. value of their
speeds?
A.
v A  vB  vC
3
B.
v A  vB  vC
3
v A  vB  vC
3
2
C.
2
v A  vB  vC
3
2
2
D.
2
2
10. The figure below is the displacement-time graph of a certain particle in a transverse wave. Given that the speed of
A.
B.
C.
D.
the wave is 0.2 m s1, what is the wavelength of the wave?
0.01 m
0.05 m
0.1 m
0.8 m
displacement / m
0.01
time / s
0
2
4
−0.01
11. A ray of light strikes the water-air boundary at an angle of incidence of 45° as shown. It is known that the
refractive index of water is 1.33. Which of the subsequent paths of the light ray is/are possible.
A. X only
B. Z only
C. X and Y only
D.
X and Z only
12. Human eye consists of a convex lens which forms an image on the retina. What is the nature of the image?
A. Real, erect and diminished
B. Real, inverted and diminished
C. Virtual, erect and diminished
D. Virtual, inverted and diminished
13. A radio station broadcasts at a frequency of 97.7 MHz. Find the wavelength of the radio wave. The speed of the
radio wave in air is 3 × 108 m s−1.
A.
0.326 m
B.
2.93 m
C
3.07 m
D.
Cannot be determined
14. A monochromatic laser is incident normally on a transmission grating. At a point X on the screen, a bright fringe
is formed due to a path difference of 2 × 10−6 m. If the wavelength of the laser is 5 × 10−7 m, what is the order of
the bright fringe at X?
A. first
B. second
C. third
D. fourth
−7
15. A monochromatic light source with a wavelength of 5.5 × 10 m is used in a plane transmission grating
3
experiment. The second-order beam makes an angle θ with the direction of incidence. If the slit separation of the
grating is 5 × 10−6 m, find θ.
A. 12.7°
B. 13.8°
C. 17.1°
D. 20.7°
16. Diffraction of light is more difficult to observe than diffraction of sound because
A. light is a transverse wave while sound is a longitudinal wave.
B. light travels much faster than sound.
C. the wavelength of light is much smaller than that of sound.
D. light is an electromagnetic wave.
17. When the loudness of a sound is increased,
A. the wavelength of the wave increases.
B.
the frequency of the wave increases.
C.
D.
the amplitude of the wave increases.
the speed of the wave increases.
18. Two identical speakers S1 and S2 are connected to the same signal generator. Two students stand at X and Y
respectively. At a certain instant, the wavefronts of the sound waves produced are as shown above. Which of the
following correctly describes the loudness of the sound heard by the students?
A.
B.
C.
D.
Student at X
soft
loud
loud
alternate loud and soft
Student at Y
loud
soft
loud
alternate soft and loud
X
Y
S1
S2
END OF SECTION A
4
INSTRUCTIONS FOR SECTION B
(1) Write your Candidate Number in the space provided on Page 1.
(2) This section carries 64 marks. Answer ALL questions.
(3) Write your answers in the spaces provided in this Question-Answer Book.
(4) Supplementary answer sheets will be provided on request. Write your Candidate Number, mark the question
number box. Tie them loosely but securely with a string INSIDE this Question-Answer Book.
(5) The diagrams in this section are NOT necessarily drawn to scale.
SECTION B Conventional Questions (64 marks)
1. A man is drilling an iron block of mass 2 kg as shown. The power of the electric drill is 2 kW. Suppose 55% of the
power has been lost as heat and increases the temperature of the iron block.
(a) Find the temperature rise of the iron block in one minute.
(3 marks)
(b) If water is dripping into the hole at a steady rate of 15 g s−1, find the temperature rise of the iron block in one
minute.
(2 marks)
(c) If water is dripping into the hole at the rate stated in (b), the temperature of the iron block will reach a steady
value eventually. Find the maximum temperature increase of the block.
(2 marks)
(The specific heat capacities of iron and water are 470 J kg−1 °C−1 and 4200 J kg−1 C−1 respectively.)
Answer:
(a) Applying E = Pt, the energy supplied to the drill is
E = 2000 × 60 = 1.2 × 105 J
Therefore, the energy lost as heat is 1.2 × 105 J × 55% = 66 000 J.
(1M)
Applying Q = mcT, we have
66 000
2  470
 70.2 C
T 
(1M+1A)
5
The temperature rise of the iron block is 70.2 °C.
(b) Applying Q = mcT, we have
66 000  2  470  ΔT 
15
 60  4200  ΔT
1000
(1M+1A)
ΔT  14.0 C
The temperature rise of the iron block is 14.0 °C.
(c) When the temperature reach a steady value, all the energy lost is transferred to the water. The maximum
temperature increase ΔT of the water is given by
15
 60  4200  ΔT
1000
ΔT  17.5 C
66 000 
(1M+1A)
Hence, the maximum temperature increase of the block is also 17.5 °C.
Read the following article about the rise of sea level and answer the questions that follow.
According to the U.S. Environmental Protection Agency (EPA) the sea levels around the world have raised fifteen to
twenty centimetres in the last century. Some scientists believe this is a consequence of the global warming. They
suggest that the rise of sea level is due to the thermal expansion of the ocean and the melting of glaciers from
landmasses (NOT from the melting of ice originally floating in the sea). For water temperature above 4C, the water
expands in volume when it is warmed and this makes the sea level rise. Moreover the rising temperature weakens the
glaciers on landmasses and causes parts of them to break off. They fall into the ocean to become icebergs and make
the sea level rises.
Besides the melting of glaciers from landmasses, will the polar ice caps melt and cause the sea level to rise
dramatically? About ninety percent of the world’s ice is located in Antarctica at the South Pole and they contribute to
seventy percent of fresh water in the world. The continent is covered with ice of an average thickness of 2,133 meters
and the average temperature there is 40C (a very rough estimation). It is far below the freezing point of water most
of the time, so there is no danger of large scale melting in the present situation. However scientists do worry about
how much ice is likely to melt and enter the ocean if the world continues to warm. It is estimated that if all of the
Antarctic ice melted, sea levels around the world would rise about 61 meters.
(a) How does the global warming lead to the rise in sea level?
(2 marks)
(b) A student claims that the energy required to change all the ice in Antarctica to 0C is less than the energy
required to melt all the 0C ice to water afterwards. Briefly comment on his claim according to information
given in the article. Given that the specific heat capacity and the specific latent heat of fusion of ice is 2100 J
kg1C1 and 3.34105 J kg1 respectively.
(4 marks)
Answer:
(a) The global warming leads to the thermal expansion of the ocean (1A) and the melting of glaciers from
landmasses (1A). Thus these result in a rise of sea level.
(b) The student is correct (1A). According to the article, the average temperature of the ice in Antarctic is 40C.
The energy needed to raise 1 kg of ice at 40C to 0C
= (2100)(40)(1)
(1M)
= 8.4  104 J
While the energy needed to melt 1 kg of 0C ice into one kilogram of 0C water
= (3.34  105)(1)
(1M)
6
= 3.34  105 J
Therefore the amount of energy used in changing 1 kg of ice at 0C to 1 kg of water at 0C is larger. Thus the
energy used in changing all the ice to water is also larger (1A).
A simplified structure of an electric oven is shown below. The heating elements are embedded in the inner metal
walls of the oven. When electric current flows through the heating elements, the walls become hot.
heating element
top
X
inner metal walls
Y
Z
bottom
insulation
heating element
(a) Name the process by which heat is transferred within the metal walls.
(1 mark)
(b) Explain, in terms of molecular motion, how heat is transferred in part (a).
(4 marks)
(c) Name the process by which heat is transferred from the metal walls to the air.
(1 mark)
(d) The surfaces of the walls are painted black. Explain why briefly.
(1 mark)
Answer:
(a) conduction
(1A)
(b) Heat is transferred within the metal walls by the collisions between free electrons and metal ions (1A). When part
of the metal is heated, the ions and free electrons there gain energy (1A). They transfer energy to the
neighbouring ions and free electrons by collisions (1A). As a result, heat is transferred from the hotter region to
the colder region (1A).
(c) conduction
(d) The walls can emit more radiation if it is painted black.
(1A)
(1A)
*A rigid vessel contains 4 moles of hydrogen (H2) and 2 moles of oxygen (O2) at a temperature of 150°C and a
pressure of 101 kPa.
(a) What is the total mass of the gas?
(1 mark)
(b) What is the volume of the vessel?
(2 marks)
(c) Suppose the gases react and change to water vapour (H2O) completely. When the water vapour cools down to
150°C, what is its pressure?
(1 mark)
The molar masses of O2 and H2 are 32 g mol−1 and 2.02 g mol−1 respectively. Take the universal gas constant R as
8.31 J mol−1 K−1.
Answer:
7
(a) The total mass is 2.02 × 4 + 32 × 2 = 72.08 g.
(b) Applying pV = nRT, we have
(1A)
10110  V  4  2 8.31 150  273
3
(1M)
V  0.2088
The volume is 0.209 m3.
(1A)
(c) Applying pV = nRT, we have
p  0.2088  2  8.31 150  273
p  33 667
The pressure is 33.7 kPa.
(1A)
A vibrator generates a wave on a string. The figure below shows the shape of the string at a certain instant.
60 cm
X
direction of
vibration
Y
direction of
wave motion
(a) Describe the motion of particles X and Y at the instant shown.
(2 marks)
(b) Particle Y completes 4 oscillations in 2 s. Find
(i) the wavelength,
(ii) the frequency, and
(iii) the speed
of the wave.
(6 marks)
Answer:
(a) At the instant shown, particle X is moving upwards (1A) while particle Y is momentarily at rest (1A).
(b) (i)
Wavelength of the wave 
(ii) Frequency of the wave 
0.6
 0.4 m
1.5
4
 2 Hz
2
(iii) Speed of the wave = fλ = 2× 0.4 = 0.8 m s−1
(1M+1A)
(1M+1A)
(1M+1A)
A stationary wave is produced on a string. The figures below show the shape of the string at time t = 0 and t = 3 ms.
vibrator
fixed end
At t = 0, all points on the string have zero displacement. At t = 3 ms, all points on the string have their maximum
displacements. The initial velocity of the left antinode is upwards.
(a) Suppose the period of the wave is longer than 3 ms.
(i) What is the earliest possible time when the string appears to be the same as
t = 0?
(1 mark)
8
(ii) What is the earliest possible time when the string looks like the figure below?
(2 marks)
(b) The frequency is gradually increased until a stationary wave with a higher frequency f1 is formed. Based on your
answer in (a), find f1.
(3 marks)
Answer:
(a) (i) t = 6 ms
(1A).
(ii) From the first two figures, we know that 3 ms is a quarter of the period of the stationary wave. It takes half
of the period for the antinodes to move from maximum displacements in one direction to maximum
displacements in the other direction. Hence the wave will move to the required position at
t = 3 + (2 × 3) = 9 ms.
(1M+1A)
(b) Let L be the length of the string. Before adjusting, the original period was 12 ms, hence the original frequency f0
was
f0 
1
Hz
12  10 3
(1M)
The original wavelength before adjustment was
0 
2
L
3
(1M)
Hence the wave speed is
v  f 00 
L
18  10 3
After the frequency is increased, the new wavelength is
1 
L
2
The wave speed remains unchanged. Therefore the new frequency is
L
3
f1   18  10  111 Hz
L
1
2
v
1.
(1A)
Two dippers S1 and S2 vibrating in phase produce a wave pattern as shown.
P
R
S1
Q
S2
The displacement-time graph of the particle P is shown below.
9
displacement / cm
1
time / s
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1
(a) Find the path difference at points
(i) P,
(2 marks)
(ii) Q, and
(1 mark)
(iii) R
(1 mark)
from S1 and S2. Give your answers in terms of wavelength  and hence state the types of interference occurring
at the points.
(b) Draw the displacement-time graphs for particles Q and R.
(2 marks)
(c) Suppose S2 is removed. State frequency and amplitude of vibration of particles
(i) P, and
(2 marks)
(ii) R.
(2 marks)
(d) Describe a method to produce an interference pattern with a single dipper. Illustrate your answer with a diagram.
(3 marks)
Answer:
2.
(a) (i)
Path difference at P  S1 P  S 2 P  4  3  
(1M)
Constructive interference occurs at P.
(ii) Path difference at Q  S1Q  S 2Q  3.5  2.5  
(1A)
Constructive interference occurs at Q.
(iii) Path difference at R  S 2 R  S1 R  3  2.5  0.5
(1A)
Destructive interference occurs at R.
(1A)
(b) The displacement-time graph for particles Q and R are as shown.
displacement / cm
Q
1
R
time / s
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
1
(2A)
(c) (i)
The frequency of vibration is 2.5 Hz.
The amplitude of vibration is 0.5 cm.
(1A)
(1A)
(ii) The frequency of vibration is 2.5 Hz.
(1A)
The amplitude of vibration is 0.5 cm.
(1A)
(d) As shown in the figure below, an obstacle with two openings is used to produce two sets of identical circular
waves (1A). A wave pattern is produced where these two set of waves overlap (1A).
10
obstacle
(1A)
lens
The lens on the watch as shown is used to produce an erect and magnified image of the date display.
(a) What kind of lens is used?
(1 mark)
(b) Is the image real or virtual?
(1 mark)
(c) Draw a ray diagram to show how the image is formed.
(3 marks)
(d) The widths of the date display and its image are 3 mm and 5 mm respectively. The distance between the lens and
the date display is 3 mm. Find
(i) the linear magnification of the image,
(2 marks)
(ii) the image distance, and
(1 mark)
(iii) the focal length of the lens.
(2 marks)
Answer:
(a) Convex lens
(b) Virtual
(1A)
(1A)
11
(c)
(3A)
image
object
F’
(d) (i)
(ii)
F
size of image
5 mm
Linear magnification = size of object =
≈ 1.67
3 mm
(1M+1A)
image distance size of image

object distance size of object
5
image distance   3
3
 5 mm
(1A)
(iii) Applying the lens formula,
1 1 1
 
u v f
1 1
1


3 5 f
f  7 .5
The focal length is 7.5 cm.
(1M)
(1A)
*A light source that includes a range of wavelength from 600 nm to 700 nm and a grating with 400 slits per mm are
used in a plane transmission grating experiment. A screen is placed 80 cm behind the grating. What is the width of
the third-order spectrum on the screen?
(5 marks)
Answer:
slit separation d 
0.001
 2.5  10 6 m
400
(1M)
For the long wavelength end of the third-order spectrum, λ = 700 nm and m = 3.
Applying d sin   m ,
(2.5  10 6 )  sin   3  (700  10 9 )
sin   0.84
  57.14
Thus the distance from the zeroth-order spectrum is
y  0.8  tan 57.14
 1.2385 m
For the short wavelength end of the third-order spectrum, λ = 600 nm and m = 3.
Applying d sin   m ,
(2.5  10 6 )  sin   3  (600  10 9 )
sin   0.72
  46.05
Thus the distance from the zeroth-order spectrum is
y  0.8  tan 46.05
 0.8300 m
Hence the width of the third-order spectrum = 1.2385 − 0.8300 ≈ 0.409 m
(1M)
(1M)
(1M)
(1A)
12
3. In an explosion, an observer standing far away first senses a slight shaking on the ground and then hears the
explosion later.
(a) Briefly explain the phenomenon.
(2 marks)
(b) What differences would be observed if the incident takes place on the Moon?
(2 marks)
Answer:
(a) In general, sound travels faster in solid than in gas (1A). Therefore, sound travelling through the ground reaches
the observer before the sound travelling in the air does (1A).
(b) The observer can only sense a slight shaking on the ground (1A) but cannot hear the sound because sound cannot
travel through vacuum (1A).
End of Paper
13