S.W.C.S. CHAN PAK SHA SCHOOL
MOCK EXAMINATION (2003 - 2004)
S.5 PHYSICS PAPER 1
25 / 3 / 2004
8.30 am - 10.00 am (1 ½ hours)
This paper must be answered in English
1. Answer ALL questions in Section A and any FOUR questions in Section B.
2. Write your answers in the answer book provided. For Section A, there is no need to start each question on a fresh page.
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 communication.
4. Take g = 10 ms-2.
5. Unless otherwise specified, all the cells are assumed to have negligible internal resistance.
6. The last page of this question paper contains a list of physics formulae which you may find useful.
Section A : (30 marks)
Answer ALL questions in this section.
1. A block of steel of mass of 100 kg at 200 oC is immersed in a mass of 15 kg of water at 15 oC. Given : The specific heat capacity of water and steel are 4200 J kg –1 oC – 1 and 450 J kg –1 oC – 1 respectively.
(a) Find the final temperature of water. [3 marks]
(b) Water is a good choice for being used as a coolant in motor cars. Explain why.
[2 marks ]
2. The eyes of a diver are 4 m below the water surface. A fish is swimming towards him at 10 m ahead. The reflective index of water is 1.33.
(a) Draw the shape of the image of the fish when the diver looks at the surface. [2 marks]
(b) Draw the path of a light ray from the mouth of the fish to show how the ray reaches the diver’s eyes. [2 marks]
(c) Describe the change of the image of the fish when the fish is swimming from A to B. The diver is looking at the image. [2 marks]
3. A mobile telephone is a small radio transmitter/receiver. The frequency used of the mobile phone is 5 GHz. The speed of light is 3 x 10 8 m s –1 and 1 GHz is 1 x 10 9 Hz.
(a) Find the wavelength of the radio wave used.
[2 marks]
(b) The diffraction of the radio wave used by the mobile phone in the city is not good. Explain why.
[2 marks]
(c) Explain how this transmission problem in real life can be solved.
[1 mark]
4. It is found that a rocket of mass 80000 kg can push out hot exhaust gas at a rate of 500 kg each second. The velocity of the ejected hot gas is 700 m s-1.
(a) Which Newton’s law is used to explain the launching of the rocket? [1 mark]
(b) What is the weight of the rocket?
[1 mark]
(c) Calculate the thrust (upward force) on the rocket.
[3 marks]
*5. The structure of a loud-speaker is shown in the figure. Describe the working principle of the loud-speaker which can produce sound. [ 5 marks ]
6. The figure shows two nuclides in a decay series.
(a) Find the mass number of nuclide A.
[ 1 mark ]
(b) Nuclide A decays into B in a series of steps. Determine the total number of alpha-particles and beta-particles emitted from A to B. [ 3 marks ]
Section B : (60 marks)
Answer ANY FOUR questions in this section
7. A student uses a lens M to see the painting of letter F which is placed 10 cm behind the lens as shown in Figure 7a. Figure 7b shows that the image of the painting. The image distance is 20 cm.
(a) State three points about the nature of the image. [ 3 marks ]
(b) Find the magnification of the object. [ 2 marks ]
(c) What is the kind of the lens? Explain briefly. [ 2 marks ]
(d) Draw a ray diagram on a graph paper to show the positions of the lens and the image formed and how the image is formed. Use a scale of 1: 5 for the object distance. [ 4 marks ]
(e) Determine the focal length of the lens from the ray diagram drawn.
[ 1 mark ]
(f) Describe how the nature of the image changes when the object is moved away from the lens. [ 3 marks ]
8. This problem is about the safety measures for driving. A car of mass 2000 kg moves at a uniform speed 36 km h-1 (= 10 m s-1) along a straight road. A lorry of mass 5000 kg moving at a uniform speed 72 km h-1 (= 20 m s-1) and are going to pass by the car. Suddenly they collide, and the collision lasts for a short time of 0.1 s. After the collision, the car moves at 72 km h-1.
(a) Consider the collision.
(i) Find the speed and direction of the lorry after the collision. [ 3 marks]
(ii) Is the collision elastic? Explain. [ 3 marks]
(b) The safety belt is a useful design used in vehicles during a collision.
(i) What is the use of a safety belt? [ 1 mark]
(ii) What is the feature of a safety belt? [ 1 mark]
(iii) Explain why the feature in (ii) can lessen the degree at which the passengers are hurt. [ 1 mark]
(iv) The driver in the car has a mass 50 kg while the time of contact between the safety belt and the driver is 0.3 s. Find the force exerted on the driver by the safety belt. [ 2 marks ]
(c) Other than the safety belt, there are other designs that are useful.
(i) The dividing barrier at the middle of a road is made of steel. Do you think that steel is an appropriate material? Explain. [ 2 marks ]
(ii) Suggest TWO other designs that can prevent the drivers and passengers from being seriously hurt. [ 2 marks ]
9. The air above Hong Kong has a volume of 4 × 1013 m3, a temperature of 27 ℃, a pressure of 100 kPa and a mass of 4.8 × 1013 kg. The specific heat capacity of air = 500 J K-1 kg-1.
(a) On a day, due to the strong illumination of the sunlight, the air absorbs a heat of 4 × 1017 J.
(i) Find the final temperature of the air. [ 3 marks ]
(ii) Hence determine the final pressure the air, assuming the volume remains unchanged. [ 3 marks ]
(iii) Actually the temperature rise is only about 3℃. Suggest TWO reasons why there exists a large difference in the temperature rise. [ 2 marks ]
(b) Due to the come of a cold current, the temperature drops from 27 ℃ by 20 ℃ while the volume drops by 2 %.
(i) Find the final pressure of the air. [ 3 marks ]
(ii) What is the heat given out? [ 2 marks ]
(iii) If the new temperature remains unchanged for a week, suggest TWO reasons why this happens. [ 2 marks ]
10. (a) Mr. Chan walks along a corridor and hears some students talking in the classroom. Explain why he can hear students talking although he cannot see them.
[ 3 marks ]
*(b) Use the following apparatus to describe an experiment which can be performed in the laboratory to show that sound is a longitudinal wave.
Match Candle Loud-speaker Signal generator
[ 5 marks ]
(c) A piece of string 2.5 m long carries a standing wave as shown.
(i) What is the wavelength of the standing waves? [ 1 mark ]
(ii) If the wave travels with a velocity of 50 m s-1 along this string, what is its frequency of oscillation? [ 2 marks ]
(iii) What is the wavelength of the sound in air produced by the vibrating string? Given that the velocity of sound air is 330 m s-1. [ 2 marks ]
(iv) Find the new frequency of vibration of the string if there is two loops is formed. [ 2 marks ]
11. (a) A GM counter is placed near a sample of radioactive source and the count rate measured are listed as follow.
Count rate / counts per min / 902 / 755 / 659 / 562 / 499 / 441 / 378 / 340 / 301
(i) Plot a graph of the count rate against time. Use a scale of 1 cm to 5 mins and a scale of 1 cm to 50 counts per min. [ 5 marks ]
(ii) Find the background count rate from the graph. [ 1 mark ]
(iii) What is meant by “ half-life ”? Find the half-life of the sample from the graph.
[ 2 marks ]
*(b) What are differences in the shape of the tracks of the alpha particles and beta particles in diffusion cloud chamber. Explain briefly. [ 5 marks ]
(c) State two application of radioisotopes. [ 2 marks ]
End of paper
Setter : Wong wing kee
Advisor : Tang tai ming
S.W.C.S. CHAN PAK SHA SCHOOL
MOCK EXAMINATION (2003 - 2004)
S.5 PHYSICS PAPER 1
marking Scheme
1. (a) heat released from steel = heat absorbed by waterm c ( T2 – T ) = m’ c’ ( T – T1 )
100 x 450 x ( 200 – T ) = 15 x 4200 x ( T – 15 )
T = 92.1 oC
(b) Water has a very high specific heat capacity.
Water can take in a lot of energy with only a small temperature rise. / 1M
1A
1A
1M
1M
2. (a)
(b)
(c) The image of the fish suddenly disappears from mouth to tail when it is swimming towards the diver. The image of the fish suddenly appears from mouth to tail when it is swimming away from the diver at the other side. / 1A – same
size
1A– inverted
1A- reflection
1A – line to the image
1M– disappear
1M– appear
3. (a) Apply v = f l
3 x 10 8 = (5 x 10 9 ) l
l = 0.06 m
(b) The wavelength is very small and is not comparable with the size of buildings. Thus, diffraction of the radio wave used is not good.
(c) By hundred of cell transmitters are set up as hexagons covering the whole of area. / 1M
1A
1M
1M
1M
4. (a) Newton’s 3rd Law, action and reaction.
(b) Weight = 80000 x 10 = 800000 N
(c) In one second, mass of gas out = 500 kg
the momentum change of gas = 500 x 700 = 350000
The thrust = rate of change of momentum = 350000/1
= 350000 N / 1M
1A
1M
1A
1A
5. An alternating current passes through the coil.
As the current flows forwards and backwards, magnetic force is induced on the coil.
Thus the coil is pushed in and out.
This makes the diagharm vibrate and vibrate the air to produce sound waves. / 1M
1M
1M
1M
1C
6. (a) The mass number of A is 136 + 86 = 222
(b) The mass number of B is 206
The number of alpha-particles is (222-206) / 4 = 4
The number of beta-particles is 4 x 2 – ( 86 – 82 ) = 4 / 1A
1A
1A
1A
7. (a) erect, virtual and magnified
(b) m = v /u
= 20 /10
= 2
(c) convex lens. It is because the image is virtual and magnified.
(d)
(e) From the graph, the focal length is 20 cm. (18 cm – 22 cm )
(f) Firstly, it remains unchanged.
Suddenly, it becomes real and inverted but it is still magnified.
Finally, it becomes real, inverted and smaller and smaller. / 1A,1A,
1A
1M
1A
1A,1M
1A– Lens
1A– object and image
1A– optical centre ray
1A– parallel ray
1M
1M
1M
1M
Marks distribution
Qn. 1 (4)Qn 2 (5)
Qn 3(5) L / Mobile phone, diffraction
Qn 4 (5) L / Rocket motion Newton’s 3rd law and 2nd law
Qn 5 (5)
Qn 6 (5)
Qn 7 (15)
Qn 8 (15)
Qn 9 (15)
Qn 10 (15)
Qn 11 (15)A / Electronic water tape.
2003
Qn 2 (6) L / Refraction of light
Qn 3(5) A / Impact force ( momentum)
Qn 4 (5) L / P-V laws
Qn 5 (4) / Interference of sound
Qn 6 (6) A / Motor and dynamo
Qn 7 (15) A / Ultrasonic application of checking cracks.
Qn 8 (15) A / Heat capacity of steam iron, V = IR, 220 => 110, L N E
Qn 9 (15) / Hazards of radiations, half-life, reaction equation. Arguments of nuclear engy
Qn 10 (15) A / Electric car, P = I V, cost of electricity.
Qn 11 (15) L / Landing in Mar. equations of motion, v-t graph of bouncing from the surface
2002