Paper 2 Nov 2000 Physics

Centre Number

Candidate Number

Candidate Name

UNIVERSITY OF CAMBRIDGE LOCAL EXAMINATIONS SYNDICATE Joint Examination for the School Certificate and General Certificate of Education Ordinary Level

5054/2

PHYSICS PAPER 2 Theory Thursday

9 NOVEMBER 2000

1 hour 45 minutes

Candidates answer on the question paper. Additional materials: Answer paper Electronic calculator and/or Mathematical tables Protractor Ruler 300 mm

TIME

1 hour 45 minutes

INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page and on any separate answer paper used. Section A Answer all questions. Write your answers in the spaces provided on the question paper. Section B Answer any two questions. Write your answers on the lined pages provided and, if necessary, continue on the separate answer paper provided. At the end of the examination, 1.

fasten any separate answer paper used securely to the question paper,

2.

enter the numbers of the Section B questions you have answered in the grid below.

INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. Candidates are reminded that all quantitative answers should include appropriate units. Candidates are advised to show all their working in a clear and orderly manner, as more marks are awarded for sound use of physics than for correct answers.

FOR EXAMINER’S USE Section A Section B

TOTAL

This question paper consists of 12 printed pages and 4 lined pages. SJF1378 QK07960/7 © UCLES 2000

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2

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Section A Answer all the questions in this section.

1

Fig. 1.1 shows the path of a ball thrown into the air. C B

A D

Fig. 1.1 (a) (i) (ii)

State at which point A, B, C or D the ball travels the slowest. ………………… Explain your choice in (i). You should write about the kinetic energy and the potential energy of the ball. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [3]

(b) The mass of the ball is 0.20 kg. At point A, the ball has kinetic energy 2.5 J. Taking the gravitational force on a mass of 1.0 kg to be 10 N, calculate (i)

the weight of the ball,

weight = ………………………… (ii)

the speed of the ball at point A.

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speed = ………………………… [4]

3 2

For Examiner’s Use

Fig. 2.1 shows a catapult used to project an object. Force F pulls back the object, creating tension in the rubber cords.

rubber cord

object

F rubber cord

direction of tension force

Fig. 2.1

60°

direction of tension force

Fig. 2.2

(a) The tension force in each rubber cord is 20 N and the two cords are at 60° to each other. Fig. 2.2 shows the direction of the two tension forces acting on the object. By making a scale drawing on Fig. 2.2, or otherwise, find the resultant of these two tension forces acting on the object. If you draw a scale drawing, state the scale that you use.

resultant force = ………………………… [3] (b) When the object is pulled back, the average value of the force F is 16 N and the object moves a distance 0.20 m in the direction of F. Calculate the work done. State clearly the equation that you use.

work done = ………………………… [2]

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4 3

For Examiner’s Use

This question is about the diffusion of gases. colourless gas

glass plate

brown gas

Fig. 3.1 Fig. 3.1 shows two cylinders. One cylinder contains a colourless gas and the other a brown gas. The glass plate is removed and the cylinders brought together. After several hours, the gases are found to be mixed together. (a) By writing about molecules, explain why the gases mix together. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2] (b) Explain why the mixing takes several hours. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [1]

4

Fig. 4.1 shows an object AB near a thin converging lens. The principal foci of the lens are at

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5

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F and F'.

A

F'

F

B

Fig. 4.1 (a) On Fig. 4.1, draw rays to find the positions of the images of the points A and B. (b) (i)

[3]

When white light passes through a prism, dispersion of the light occurs and a spectrum is formed. Explain what is meant by the dispersion of light. .................................................................................................................................. ..................................................................................................................................

(ii)

Fig. 4.2 shows a ray of white light incident at 90° to side A of a glass prism.

white light

side A

side B

Fig. 4.2 Draw rays to show the passage of the light through the prism and out of the prism at side B. [4] 5

Fig. 5.1 shows steam passing into a jug to warm up some cold water. In this question, you

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may ignore any heating of the atmosphere.

steam

cold water

Fig. 5.1 Pure steam enters at 100 °C and the jug initially contains 500 g of water at 20 °C. Eventually, the water in the jug reaches a temperature of 100 °C. The specific heat capacity of water is 4.20 J/(g °C) and the specific latent heat of vaporisation of water is 2250 J/g. (a) State what is meant by the specific latent heat of vaporisation of water. .......................................................................................................................................... ..................................................................................................................................... [2] (b) Explain why the mass of water in the jug increases. .......................................................................................................................................... ..................................................................................................................................... [1] (c) Calculate the energy needed to warm 500 g of water from 20 °C to 100 °C.

energy = ………………………… [2] (d) Calculate the final mass of water in the jug, when its temperature has reached 100 °C.

mass = ………………………… [2] 5054/2 W00

6

Plotting compasses may be used to plot magnetic fields.

7

plotting compass

For Examiner’s Use

current

Fig. 6.1

Fig. 6.2

In Fig. 6.1, four plotting compasses are shown near a wire. There is no current in the wire and the arrow in each compass points towards the North. In Fig. 6.2, the same plotting compasses are shown near a wire in which there is a current downwards. The current creates a strong magnetic field near the compasses. (a) (i) (ii)

On Fig. 6.2, draw the direction shown by the arrow in each compass. State where the magnetic field due to the current has its greatest strength. ............................................................................................................................. [3]

(b) Describe how you would use one compass to plot the lines of the magnetic field around the wire in Fig. 6.2. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[3]

7

A smoke detector contains a radioactive source that emits α-particles.

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radioactive source α-particle paths

plate

A Fig. 7.1 Fig. 7.1 shows the structure of a simple smoke detector. The α-particles ionise the air between the plates. Positive ions and negative ions are created in the air and, as a result, a current is produced in the circuit. When smoke is present, the current decreases. (a) State the nature of an α-particle. .......................................................................................................................................... ..................................................................................................................................... [1] (b) Explain why a source that emits β-particles is not used in this detector. .......................................................................................................................................... ..................................................................................................................................... [1] (c) The radioactive source that emits α-particles contains Americium-241. A nucleus of Americium-241 is represented as

241 95 Am.

Describe the structure of an atom of Americium-241. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [3]

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For Examiner’s Use

Fig. 8.1 shows how the current in the filament of a lamp depends on the potential difference across it. 0.35 0.30 0.25 0.20 current/A 0.15 0.10 0.05 0 0

1

2

3

4

5

potential difference / V Fig. 8.1 (a) Calculate the resistance of the filament when the current is 0.25 A. Give your answer to an appropriate number of significant figures.

resistance = ………………………… [3] (b) Explain how Fig. 8.1 shows that the resistance of the filament increases with temperature rise. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [2]

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10 Section B Answer two questions from this section. Use the lined pages provided and, if necessary, continue on the separate sheets available from the Supervisor.

9

A lamp marked 6.0 V, 36 W is to be run from a power supply. The power supply can provide either direct current or alternating current. (a) To operate at normal brightness, the lamp needs an effective potential difference across it of 6.0 V. (i)

Explain what is meant by potential difference.

(ii)

Calculate the current through the lamp when it is operating normally.

(iii)

Explain why the lamp should not be connected directly across a 10 V power supply.

[6]

(b) Two students, A and B, suggest different ways to run the lamp at normal brightness using a 10 V power supply. (i)

Student A suggests that the lamp is used with a series resistor R, as shown in Fig. 9.1.

R

power supply 10 V

lamp 6.0 V, 36 W

Fig. 9.1 State values for the potential difference across resistor R and the current through it, when the lamp is at normal brightness. (ii)

(iii)

Student B suggests that a transformer is used to transform the power supply voltage down to 6 V. 1.

Draw a labelled diagram of a transformer that could be used with a 10 V a.c. supply to operate the lamp normally. Suggest suitable values for the number of turns in each coil.

2.

Explain how the transformer produces an output voltage.

Suggest and explain which student, A or B, has the better solution.

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[9]

11 10 (a) Sound is a longitudinal wave. Explain, with the aid of a diagram, what is meant by this statement. [4] (b) Sounds can be used to produce waveforms on the screen of a cathode-ray oscilloscope. Sound from a simple whistle produces the waveform shown in Fig. 10.1.

Fig. 10.1 Describe how you would use a cathode-ray oscilloscope and other apparatus (i)

to produce such a display from a whistle,

(ii)

to measure the time of one oscillation of the sound emitted by the whistle. In your account, you should • state the audible frequency of the whistle to be used, • draw a diagram of the apparatus, • explain how to adjust the cathode-ray oscilloscope to display the waveform, • state the readings to be taken, • explain how the time for one oscillation is found from these readings.

(c) (i)

[7]

Fig. 10.2 shows the waveform produced on an oscilloscope screen by a sound.

Fig. 10.2 State how you can tell from the waveform that

(ii)

1.

the loudness of the sound is decreasing,

2.

the frequency of the sound is constant.

The separate waveforms of two whistles of different frequencies are obtained on the oscilloscope screen at the same time. Draw the two waveforms you would expect to see. Label the waveform that has the higher frequency. [4] [Turn over 5054/2 W00

12 11 (a) Ripple tanks may be used to produce plane water waves. Draw a labelled diagram of a ripple tank used to produce plane water waves. Your diagram should show how the waves are made and how they are observed. [4] (b) Water waves may be refracted at a boundary.

D

boundary

C B A

Fig. 11.1 (full scale) Fig. 11.1 shows four wavefronts of a water wave incident on a boundary. As the wave crosses the boundary, the wave is refracted. (i)

Copy Fig. 11.1 and draw the wavefronts after refraction, to the right of the boundary.

(ii)

Describe how the ripple tank in (a) could be used to produce this refraction.

(iii)

State why the water waves are refracted. [5]

(c) The wavefronts shown in Fig. 11.1 are drawn full-scale. It takes 0.75 s for a wavefront to travel from A to D. Using measurements taken from Fig. 11.1, determine, for this wave, (i)

the speed,

(ii)

the wavelength,

(iii)

the frequency. [6] 5054/2 W00

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