SHATIN TSUNG TSIN SECONDARY SCHOOL Mock Examination Physics I Date:23 March-2005

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S.5 2004-2005 Mock Examination - Physics II P.1 S5 Marks: 96 marks SHATIN TSUNG TSIN SECONDARY SCHOOL 2004-2005 Mock Examination Physics I Date:23 March-2005 Time Allowed: 1hour 45 mins.

1 S Mock Examination - Physics II P.1 S5 Marks: 96 marks SHATIN TSUNG TSIN SECONDARY SCHOOL Mock Examination Physics I Date:23 March-2005 Time Allowed: 1hour 45 mins. Instructions: 1. This paper consists of TWO sections, Section A and Section B. Section A carries 55 marks and Section B carries 41 marks 2. Answer ALL questions in each section. Write your answers in the spaces provided in this Question- Answer Book. Supplementary answer sheets 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 communication. 4. Unless otherwise specified, numerical answers should be either exact or correct to 3 significant figures. 5. Take g = 10 m s Unless otherwise specified, all the cells are assumed to have negligible internal resistance. 7. Only calculators approved by HKEAA can be used. 8. The diagrams in this paper are NOT necessarily drawn to scale. Section A (55 marks) Answer ALL questions in this section and write your answers in the spaces provided. Question No Marks Infra-red thermometer The infra-red thermometer that the general public know best could be the one in Figure 1a. We know that it is used to measure body temperature. How does an infra-red thermometer measure temperature? It is found that objects at different temperatures emit different amounts of radiations. For example, a hot object emits more infra-red radiation than a cold object. Hence, by measuring the intensity of infra-red radiation emitted by an object, infra-red thermometer can find out temperature of the object. As a result, no contact between objects and infra-red thermometers is required in measuring temperature. Because of this property, infra-red thermometers and thermometers based on similar principle are also called non-contact thermometers. Since infra-red thermometers do not touch objects when they measure temperature, they do not take energy away from the objects and hence do not change the temperature distribution of the objects. Also, they can respond rapidly to the temperature change of the objects. Figure 1a Apart from measuring body temperature, non-contact thermometers are widely used in manufacturing industry, like metals and glass, in hospitals, in fire-fighting, etc. (Reference: (a) How does an infra-red thermometer measure temperature? (1 mark) (b) In the article, what are the advantages of using non-contact thermometers?

2 S Mock Examination - Physics II P.2 (c) Give an example of contact thermometers. What limits the temperature range measured by that thermometer? 2. When somebody suffers from a fever, the elderly Chinese often suggest covering his body with thick quilts. They maintain that one will feel much better after sweating. (a) A person perspires 2 litres (2 kg) of sweat/water in 1 hour. How much energy is required to evaporate this amount of sweat? (Specific latent heat of water is 2260 kj/kg) ( 2 marks) (b) If this amount of energy is not removed from the body by perspiration, by how much would the body temperature of a person of mass 60 kg rise? The average specific heat capacity of the human body is 3500 J kg 1 C 1? 3 In a volley-ball game, Jenny serves by throwing a volley-ball upwards and hitting it at its highest point. Jenny throws the ball upwards at 6 m s 1. Take upward direction as positive. (a) Find the time at which the ball reaches the highest point. Hence, sketch the velocity-time graph of the ball before it is hit. What is the physical meaning of the slope of the graph? (5 marks) (b) From (a), find how high the ball rises.

3 S Mock Examination - Physics II P.3 4 A student arranges 50 dominoes on a horizontal table. Each of them is separated by 5 cm. The first domino is pushed so that it falls and hits the next domino. The fall-and-hit sequence repeats itself and it takes 10 s for all dominoes to fall. 5 cm The student calls it a pulse of 'domino wave' as he thinks that it is a kind of wave motion. (a) Calculate the speed of this pulse of 'domino wave' by using the definition of wave speed. (b) Suggest one reason why 'domino wave' is actually NOT a wave.

S.5 2004-2005 Mock Examination - Physics II P.

'ping' it sends out and the 'echo' it receives. The speed of sound in water is 1400 m s 1. Figure 5a ping echo submarine Figure 5b (a) An 'echo' is received 1.

4 S Mock Examination - Physics II P.4 5 Figure 5a shows a fast attack submarine USS Salt Lake City (SSN 716), and Figure 5b shows how it detects the position of an enemy ship by finding the time difference between the 'ping' it sends out and the 'echo' it receives. The speed of sound in water is 1400 m s 1. Figure 5a ping echo submarine Figure 5b (a) An 'echo' is received 1.5 s after a 'ping' is transmitted. What is the distance of the enemy ship from the submarine? (b) The frequency of the 'ping' signal is 2000 Hz. (i) What is the wavelength of the 'ping' signal in water? (ii) Explain why signals of this frequency are unable to locate the position of small objects, whose sizes are comparable to a football.

S.5 2004-2005 Mock Examination - Physics II P.5 6 The following figure shows an electrostatic spray painting a car body. The paint droplets are given a positive charge.

What should be the charge of the car body? Explain briefly. (3 marks) 7 In Hong Kong, the mains supply is at 220 V.

5 S Mock Examination - Physics II P.5 6 The following figure shows an electrostatic spray painting a car body. The paint droplets are given a positive charge (a) The electrostatic spray can produce a more even coating than uncharged sprays. Explain briefly. (b) To improve the paint spraying process, the car body is charged. What should be the charge of the car body? Explain briefly. (3 marks) 7 In Hong Kong, the mains supply is at 220 V. The following figure shows a household electric wiring plan with sockets viewed from the front. (a) Name the wires X and Y. (b) Suggest one reason why sockets are connected in parallel. (1 mark) (c) The following electrical appliances are plugged into sockets. Rice cooker: '220 V, 1000 W' Kettle: '220 V, 2000 W' (i) If these appliances are switched on, calculate the current drawn from the mains. (4 marks)

S.5 2004-2005 Mock Examination - Physics II P.6 (ii) If the cost of electrical energy is $0.9 per kw h, find the cost to switch on these appliances for 10 hours.

6 S Mock Examination - Physics II P.6 (ii) If the cost of electrical energy is $0.9 per kw h, find the cost to switch on these appliances for 10 hours. (d) What is the purpose of the fuses in a consumer unit ('fuse box') (1 mark) (e) State one advantage of using ring main. 8 This question is about radioactivity. (a) A radioactive source X decays by emitting γ rays. The following graph shows how the corrected count rate of X changes with time. corrected count rate / counts per min time / hour (i) Explain what is meant by the corrected count rate. (ii) What is the half-life of X? (Show your work in the graph if necessary)

7 S Mock Examination - Physics II P.7 (iii) After emitting γ rays, how would the atomic number and mass number of X change? (iv) Describe how you can check if the source emits γ radiation only, without α and β radiation. (b) Radioactive materials are used in hospitals as tracers. The radioactive tracer is injected into the patient's blood stream. After a short time, a camera is used to detect the radiation coming from the patient's body. (i) State TWO reasons why α source is never used for this purpose. (ii) By considering the half-life of X, state whether or not it is suitable as tracers.

8 S Mock Examination - Physics II P.8 Section B (41 marks) Answer ALL questions in this section and write your answers in the spaces provided Question No Marks In a snooker game, Goerge hits the white ball and then the white ball hits the coloured ball head-on. The coloured ball later falls into the pocket. Assume that all balls have the same mass. (a) By considering conservation of momentum, write an equation relating the velocities of the balls before and after the head-on collision. Define the symbols in the equation clearly. (3 marks) (b) Show that, if the collision is elastic, the white ball will NOT follow the coloured ball to fall into the pocket. (4 marks)

S.5 2004-2005 Mock Examination - Physics II P.9 10 Figure 10a shows sunlight shining into a room through a window.

$2 Light waves spread when passing through the window. (1 mark) (b) Explain briefly why diffraction is not observed in this case.$

9 S Mock Examination - Physics II P.9 10 Figure 10a shows sunlight shining into a room through a window. Figure 10a (a) Which of the following statements is more suitable in describing the behavior of sunlight in this case? 1 Light rays travel in straight lines. 2 Light waves spread when passing through the window. (1 mark) (b) Explain briefly why diffraction is not observed in this case. (c) Hence, explain briefly why we usually use the ray model, rather than the wave model, to explain daily phenomena of light. 11. The following figure shows a small block M of mass 1 kg being transported across a small hill along ABC by an applied force F, which is always parallel to the path. The speed of M is kept constant throughout the journey and the friction between the block and the road is 2.60 N. F B M 10 m A C (a) Consider the journey from A to B. (i) Draw a labelled force diagram to show all the forces acting on the block. (4 marks)

10 S Mock Examination - Physics II P.10 (ii) Find the applied force F. (iii) Find the work done by F. (b) Consider the journey from B to C. (i) Determine the direction and magnitude of the applied force F. (ii) Find the work done by F. (1 mark) (c) A student says that both the potential energy and the kinetic energy of the block M are the same at A and C. Therefore the total work done by F in transporting the block from A to C is zero. Comment on this statement. (3 marks)

11 S Mock Examination - Physics II P In the following figure, a magnet is tied to a spring. When the magnet is pulled down and released, it oscillates above a solenoid. *(a) It is found that the pointer of the galvanometer swings. Explain briefly. (5 marks) (b) A student states that the current passing through the galvanometer is zero when the magnet is at its lowest point. Comment on his statement. (3 marks) (c) Suggest THREE methods to increase the current in the solenoid. (3 marks) (d) Using conservation of energy, explain why the magnet oscillates with decreasing amplitude. (1 mark)

12 S Mock Examination - Physics II P.12 (e) The galvanometer is now replaced by an a.c. source of frequency 1 Hz. (i) Describe what happens to the magnet. (ii) What will happen to the magnet if the frequency of the source is increased to 50 Hz? (1 mark) -- End of Paper--

Mock-CE PHY PAPER 1 MOCK EXAMINATION PHYSICS PAPER 1. Question-Answer Book. (1¾ hours) This paper must be answered in English. Name.

Mock-CE PHY PAPER 1 MOCK EXAMINATION PHYSICS PAPER 1. Question-Answer Book. (1¾ hours) This paper must be answered in English. Name. Mock-CE PHY PAPER 1 Name Class Class number MOCK EXAMINATION PHYSICS PAPER 1 Question-Answer Book (1¾ hours) This paper must be answered in English 1 Write your Name, Class and Class number in the spaces