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CCC HOH FUK TONG COLLEGE

MOCK EXAMINATION 2001-2002

PHYSICS PAPER I

SECONDARY:5 FULLMARK:90

TIME:8:30-10:00 (1.5 hrs)DATE: 26/3/2002

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 with asterisk(*). In answering these parts, candidates are required to give paragraph-length answers. In each of these parts, one is allocated to assess candidates’ abilities in effective communication.
  4. Take g=10ms-2
  5. Unless otherwise specified, all cells are assumed to have negligible internal resistance.

Section A (30 marks)

Answer ALL questions in this section.

1. An unloaded truck X of mass m kg is moving on a straight road. It hits on another loaded truck Y of mass 2m kg which is at rest. They stick together and move at 14ms-1 just after the impact.

(a) Find the change of the momentum of Y.(2 marks)

(b) By considering the speed of X before it hits Y, explain why the driver violates the Hong Kong traffic ordinance (breaks the law). (3 marks)

(1ms-1 = 3.6 kmh-1)

2. A pressure cooker contains of air at a pressure of Pa at .

(a) The cooker is heated from to . What is the new pressure inside the cooker? (3 marks)

(b)Then, oil of is forced into the cooker and there is no air leaking. What is the final pressure? (2 marks)

(Assume oil will not be changed into gas)

3. (a) What type of lens must be used in a simple camera?(1 mark)

*(b) If a photographer has taken a near object, he now wants to take a very farobject. How should he move the lens for a clear image? (3 marks)

(c) If he wants to take a sunset scene, what should be the distance between the lens and the film? (1 mark)

4. A cork floats on water and it moves up and down in the same position 2 times a second due to a water wave. The distance of a successive peak and trough of the wave is measured to be 8 cm.

(a)What is the wavelength of the water wave?(1 marks)

(b)What is the period of the oscillation of the cork?(2 marks)

(c)What is the speed of the wave?(2 marks)

5. A model power station transmits electrical power to a house. The power consumption and the voltage of the house are 100W and 20V respectively. The total resistance of the transmission cables is 4Ω.

(a) Find the current flowing through the cables.(1 mark)

(b) Find the power loss in the cables.(1 mark)

(c) What is the voltage drop in the cables.(2 marks)

(d) What should be the power output of the power station(1 mark)

  1. Explain the following phenomena:

(a) A beam of light bends slightly when travelling a long distance in the air.

(2 marks)

*(b) A bag of cotton wool falls slower than a steel ball of same mass when they are released from the top of a building at the same time. (3 marks)

Part B (60 marks)

Answer any FOUR questions in this section. Each question carries 15 marks.

  1. (a) State two natures of images formed by eye and camera.(2 marks)

(b) A person cannot see objects nearer than 50 cm clearly.

(i) What kind of eye defect is he suffering from?

Illustrate your answer with the aid of a ray diagram.(4 marks)

(ii) Name two causes of such an eye defect.(2 marks)

(iii) What kind of lens should he wear to correct the defect?

Draw a ray diagram to show how the correction is made.(4 marks)

(c) If a camera cannot focus objects with distances shorter than 50cm, what lens should be used to replace the original lens, a thicker or thinner lens? (1 mark)

(d) State a difference between a camera and a human eye when focusing objects of different distances. (2 marks)

  1. (a) In an experiment at an accident research unit, a moving car P was made to collide with a second stationary car Q. On impact, the two cars stuck together and then skidded to rest.

The graph below shows the velocity of car P throughout the experiment.

A / B
C
D

(i)Which section of the graph corresponds to the collision between the cars? (2 marks)

(ii)Which section of the graph corresponds to the cars kidding to rest?

(1 mark)

(iii)State the velocity of car Q at the time corresponding to point B on the graph. (1 mark)

(b) A dummy of mass 70kg was firmly fixed in car P using a seatbelt. Information from the graph indicates a deceleration 45ms-2 during the collision.

(i) Calculate the force exerted by the seatbelt on the dummy.(2 marks)

* (ii) Describe carefully what would have happened to the dummy if it

had not been wearing a seatbelt. Explain your answer in terms of Newton’s law of motion. (3 marks)

(c) (i) Calculate the deceleration of the cars as they skidded to rest.(3 marks)

(ii) The experiment was repeated with identical cars when the road was wet. What difference would you expect to find in the section CD of the graph? Explain your answer? (3 marks)

  1. A student carries out an experiment to investigate the thermal properties of an unknown liquid X. The liquid is heated by an electric stove of constant power. The total mass of the liquid and the set-up is obtained by an electronic balance as shown below.

(a)The teacher suggests three precautions to the student.

(i)Insert a stirrer into the beaker and stir the liquid thoroughly before each measurement.

(ii)The beaker should be wrapped with cotton wool.

(iii)The power of the stove should not be too high.

Give a reason to each of them.(4 marks)

The experiment is carried out and the following two graphs show the temperature of the liquid and reading of the balance throughout the experiment.

(b) The total mass of the beaker, rack, thermometer and the stove is 350 g. What is the initial mass of liquid X? (1 mark)

(c) Given that the power of the heater is 30 W, find the total energy supplied in the first 12 minutes. (2 marks)

(d) Determine the specific heat capacity of liquid X.(3 marks)

(e)What happens in the last 8 minutes? State the physical meaning of the temperature indicated by the horizontal level of the heating curve. (2 marks)

(f) Find the specific latent heat of vaporization of liquid X.(3 marks)

  1. Draw the circuit symbol for a NOR gate and complete the truth table for NOR gate in following format in your answer book:

Input A / Input B / Output Q
1 / 1
1 / 0
0 / 1
0 / 0

(4 marks)

The diagram shows a circuit for an automatic watering system for plants.

The soil contacts are buried in the soil near the plants. When the soil dries out, the logic state of input B changes from high (logic 1) to low (logic 0).

(a) Why is the logic state of input B low when the soil is dry?(2 marks)

(b)It gets dark and the logic state of input A changes to low (logic 0). What happens to the resistance of the LDR? (2 marks)

(c)(i) What are the logic states at Q, A and B when the watering system turns on? (3 marks)

(ii) What are the soil and light conditions when the water system turns on?

(2 marks)

(e) Describe the effect of increasing the value of resistor R1 on the behaviour of the circuit. (2 marks)

  1. The figure shows a set-up carried out in a vacuum chamber to study the radiation from a radioactive source that emits α, βand γradiation. A magnetic field (pointing into of the paper) is applied. The photographic film shows two marks P and Q after developing.

(a) Copy the figure into your answer book and sketch and label the paths of α, β and γradiation emitted from source in the figure. (3 marks)

(b) (i) Why should the experiment be placed in a vacuum chamber ?(2 marks)

(ii) Why do we use a lead box with a narrow slit?(2 marks)

(iii) Why are there only two marks on the photographic film?(2 marks)

(c) If a piece of paper is placed between the source and the photographic film, how would the marks on the photographic film be affected? (2 marks)

(d) State one other type of detector that may replace photographic film to detect radiation in this experiment. (2 marks)

(e) Give ONE application of radioactivity.(2 marks)

End of Paper I

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