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CARIBBEAN EXAMINATIONS COUNCISECONDARY EDUCATION CERTIFICATE

EXAMINATIONPHYSICSPaper 03 - General Proficiency

I hour

IA I.JI IAR Y ANONL

r0 JANUARY 2fiXl (.-'n.;

In addition to the I hour. candidates are allowed arradtng ttrne of l0 minutes. Writing ma-v beginduring the 10-minute period.

READ THE FOLLOWING DIRECTIONS CAREFULLY

Answer ANY THREE questions.

ALL WORKING MUST BE SHOWN in your answer booklet. since marks will be rwarded forcorrect steps in calculations.The use of non-programmable calculators is ailowed.Mathematical tables are provided.

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

t.)

3.4.

Copyright @ 1999 Caribbban Examinations CounciiAll riehts reserved.

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Describe an experiment to demonsrrace the interf-erence of sounddescribe the apparatus you wouid use" rhe observations you wouldexplain these observations.(a)

(c)

T. In your arcount.need to make antl( 8 marks)(b) Figure 1 below is a displacemenr-rimecertain point in air.

Displacement /mrn

graph which represents a sound wave passing u

Figure IDeduce the frequency oithe sound wave und calculate its wavelength given that the speedof sound in air is 330 m s -r. ( 5 marks)A_source of' sound is placed under water. where the speed oF sound is I.100 m s -, . as inFigure 2 below. Calculate the refractive index lor sound passing tiom water to air. and useyour result to calculate the angle of refraction in the air tor a sound wave that strikes thewlter/uir boundary ut an ungle ot'incidence ot'-{0o. Copv the diagram rnto vour .nswerbooklet and sketch the path of the sound wave. ( 7 marks)

Figure 2Total 20 marks

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{"If}RA.qYTown Senio. e jSchod -omPrahsasillZ.' ' (a) The Geiger-Marsden experiment (aipha-particle scattering experiment) supported r

nuclear model of the atom over the model that had been previously accepted. Brreflydescribe the model which was accepted ut the time of this experiment. Outline theGeiger-Marsden experiment and show how the observations support the nuclear model.. ( g marks)

(b) (i) A radioactive isorope ol lead. Pb-:l-1. emits bcta-particles which I rate-meterdetects. In four consecutive periods. the number of counl.s reccrded by the raiemerer were: 4823. 1764.4829 and -1784. Explain whv the count rate is notconstant and find the average count.

1ii) In a similar ser of measurernents 50 minutes later. the counts recorded were I216.I 169. 1225 and I 190- Find the average count rt this time and use the two vlluesyou have calculated to tind the half-lile of the source. ( 6 marks)The proron number of leud is 82 and the product of the beta-decay of Pb-l l -l is bismuth(Bi). Write down the nuclear reaction for this decay. Write down the symbol tbr anotherisotope of lead and state the number of electrorrs e neutral atom of this isotope wouldcontaln ( 6 marks)

Total 20 marks

Use the kinetic theory ol gases to explain(i) why particles o[smoke in air are seen to move in a random munner when viewetlthrough a microscope(ii) how the air in a tyre cxerts a pressure on rhe tyre wull und wlrv the pressure

increases when the temperature of the lir increuses. t 8 marks)The air in EACH of the four tyres ol a pick-up truck exerts a pressure ol 2.5.r l0-5Nm-:. Theareaofeachtyreincontactwiththegroundisll5cmrandthepressureofthe air in the tyres lehds ro a force which supports rhe weight ol'the truck. Culculate themass of the truck. (g = l0 m s-r) ( 7 marks)

(c) What effect would an increase in the temperature of the air in the tyres have on the areuof contact between the tyres and the ground? Write down TWO assumptions you havemade in your answer ( 5 marks)

Total 20 marks

(c)

(a)

P =rfb)

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4.

,.+(a) Define linear momentum, state the law of conservation oilinear momentum and descnbean experiment to demonstrate this law. ( 8 marks

(i)

(ii)

(b) A spacecraft acclerares by ejecting gases at high speed from its rockets. Use rhlaw of conservation of momentum to explain how this results in an increase ospeed of the spacecraft.A spacecraft, of mass 8 000 kg, is travelting at a constant spee.d when its rockeare turned on. The gases ar emirted at a rate of l.5kgs-landaremovingat a speed of I100 m s-r. Find the change in momentum per second of the gaCalculate the increase in velociry per secondof the spacecraft and the tonlchangin velocity if the rockets are fired for l5 seconds. The final speed of the spacecrais 1200 m s-' . What distance will the spacecraft travel in one week?AsecondspacecraftisinorbitataconstantspeedaroundtheEarth. Drawasketcto show the force or forces on this spacecraft. (12 marks

Total20 marks

terms of the energ( 2maiks(a)(b) Figure 3 below shows a simple d.c. motor connected in a circuit.

( iii)

Explain the difference between a moror and a generator inconversions involved.

(c)

Figure 3Explain why, when the switch, S, is closed. the coil rotates continuously in one directionState the direction of rotation.Identify a modification that is needed in converting the d.c motor in Figure 3 to an agenerator. ( 8 marksAnelectricmotorisoperatingonacurrentof 2.5Aatap.d. of 24OV. Itisconnecteby a long cabie to the generator. If the potential difference at the terminals of thgenerator is 250 V, determine the resistance of the cable and the loss of power in the cablWhat is the power supplied by the generaror? (10 marks

Total20 mark

Coil

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