# Physics–Paper 2 June 1988

CARIBBEAN EXAMINATIONS COUNCIL

SECONDARY EDUCATION CERTIFICATE EXAMINATION

PHYSICS

Paper 2

General Proficiency

1 1/4 hours

1. You MUST use this answer booklet when responding to the questions. For each question write your answer in the space indicated and return the answer booklet at the end of the examination.
2. ALL WORKING MUST BE SHOWN IN THIS BOOKLET, since marks will be awarded for correct steps in calculations.
3. Attempt ALL questions.
4. The use of calculators is allowed.
5. Mathematical tables are provided.

DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO

1. A girl on a bicycle accelerates uniformly from rest and reaches a velocity of 10 m s-1 after 4 s. She continues at this speed for a further 24 s and then decelerates uniformly to come to rest in 5 s.

(a) On the axes below, sketch a velocity-time graph to illustrate the girl’s journey.

(4 marks)

(b) Find the initial acceleration and the final deceleration of the girl.

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(3 marks)

(c) How far did the girl travel?

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(3 marks)

(d) What was the average velocity for the first 10 s of the journey?

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(3 marks)

(e) In the space below, sketch the displacement-time graph for the whole journey?

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(4 marks)

(f) If the mass of the girl and the bicycle is 80 kg, how much useful work does she do in reaching a velocity of 10 m s -1 ?

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(3 marks)

Total 20 marks

(2) (a) An air-conditioner is a device used for cooling buildings. An insurance company plans to build a block of offices which is to be air- conditioned. State and explain THREE features of the design which could reduce the amount of solar radiation entering the building during the day and hence reduce the cost of the cooling building.

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(6 marks)

(b)

An air-conditioner, (see diagram above), works in such a way that a fluid is evaporated on the room side of the conditioner and, with the help of the compressor, it is condensed back to the liquid state outside the room.

Explain how this process is able to transfer thermal energy from the room to the outside.

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(4 marks)

(c) The heat capacity of a room is 3 x 10JK1 The room is cooled by an air-conditioner extracting heat at a rate of 500W. By how much will the temperature of the room fall in five minutes?

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(4 marks)

(d) Architects quote the power of air-conditioning systems in a strange unit called the ‘ton’ of air conditioning. A system is rated at 1 ‘ton’ if it extracts the same amount of heat in 1 day as 1 ton of ice would need to melt at its normal melting point.

Using the data provided on the cover page, calculate how many kilowatts are equivalent to the ‘ton’ of air-conditioning.

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(6 marks)

Total 20 marks

3.

The diagram above represents an atom.

(a) (i) Identify the components: X, Y and Z.

X______________________

Y______________________

Z______________________

(3 marks)

(ii) State whether or not the atom is neutral. Explain your answer.

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Record the mass (nucleon) number of the atom.

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(3 marks)

(iii) Draw a similar diagram to represent an isotope of the atom in (ii) , and record its mass (nucleon) number.

(3 marks)

(b) (i)

The sequence above represents the radioactive decay of a thorium source. It is known  that ALL the radioactive emissions are obtained from the source. Enter, above each arrow, the symbols for the radiations that are likely to be emitted.

(4 marks)

(ii) If someone is exposed to all three radiations from the thorium source, which one do you think is most likely to cause the greatest harm? Explain your answer.

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(3 marks)

(iii) Calculate the half-life of a radioactive substance whose activity falls to 25% in 10 hours.

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(2 marks)

(iv) The activity of a substance falls from 3000 Bq to 750 Bq in 10 hours. What is its activity after a further 15 hours.

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(2 marks)

Total 20 marks

4. (a) State the MAIN differences between the magnetic properties of iron and steel.

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(2 marks)

(b)

The diagram above represents the circuit for the operation of an electric bell.

(i) Identify the components of A and B.

A____________________________________

B____________________________________

(ii) Describe clearly the function of EACH of the components X, Y, and Z.

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(6 marks)

(c)

The circuit above was connected by a student in an attempt to measure the resistance of the resistor Rx. The battery and the ammeter had negligible resistance.

(i) What is wrong with the circuit?

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( 5 marks)

(ii) Redraw the circuit as it should have been connected.

(2 marks)

(iii) If the current through Rx when the circuits correctly is correctly wired is 0.16 A, what is the voltmeter reading?

(3 marks)

Total 20 marks

5.

The diagram above represents a vibrating source, S, generating ripples in a shallow trough of water at a rate of 5 per second. The wavelength of the ripples is 1.5 cm.

(i) Describe the motion of the source S and state its frequency.

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(2 marks)

(ii) With reference to the diagram above, write TWO statements describing the motion and frequency of a particle, P, of the medium (water).

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(2 marks)

(iii) Calculate the velocity of the travelling wave.

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(2 marks)

(iv) State TWO differences between travelling and standing waves.

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(2 marks)

(v) With reference to the diagram above , mention ONE step that could be taken to obtain a standing wave from the travelling ripples in the trough.

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(1 mark)

(b)

The figure above shows wave fronts striking a boundary, AB, between deep and shallow water. The distance apart of these wave fronts is 1.5 cm (drawn to scale). The angle of incidence, Ѳ, is such that

The refractive index of waves travelling into the shallow water is 2.

(i) Calculate the wavelength in shallow water.

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(2 marks)

(ii) Complete the diagram above to show the refracted wave fronts with their correct separation.

(3 marks)

(iii) Calculate the value of ф, the angle of refraction of the waves.

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(3 marks)

(iv) Calculate the velocity of the wave fronts in shallow water if the velocity in deep water is 4 cm s-1.

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(3 marks)

Total 20 marks

END OF TEST

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