Paper 3 Nov 2000 Physics

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

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PHYSICS PAPER 3 Practical Test Thursday

2 NOVEMBER 2000

2 hours

Candidates answer on the enclosed answer booklet. Additional materials: As listed in Instructions to Supervisors Electronic calculator and/or Mathematical tables Graph paper

TIME

2 hours

INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces provided on the answer booklet. Answer all questions. Write your answers in the spaces provided in the answer booklet. For each of the questions in Section A, you will be allowed to work with the apparatus for a maximum of 20 minutes. For the question in Section B, you will be allowed to work with the apparatus for a maximum of 1 hour. You are expected to record all your observations as soon as these observations are made. All of your answers should be written in the answer booklet; scrap paper should not be used. An account of the method of carrying out the experiments is not required. At the end of the examination, hand in only the answer booklet. INFORMATION FOR CANDIDATES Graph paper is provided in the enclosed answer booklet. Additional sheets of graph paper should be used only if it is necessary to do so and attached firmly to the answer booklet.

This question paper consists of 5 printed pages, 3 blank pages and an inserted answer booklet. MML LOC 2301 5/99 QK07964 © UCLES 2000

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2 Section A Answer all questions in this section.

1

In this experiment, you will determine the density of the glass from which some spheres are made. You have been given 10 glass spheres in a small dish, a measuring cylinder and a quantity of water in a beaker. A top-pan balance is available. (a) Pour 50 cm3 of water into the measuring cylinder. Carefully roll a sphere down the side of the cylinder so that the level of water rises. Repeat this with as many spheres as possible to give a large rise in the level of water. All the spheres used in the cylinder must be completely submerged in the water. (b) Record (i) the number N of spheres in the measuring cylinder, (ii) the total volume VT of the contents of the cylinder. (c) Calculate (i) the volume V occupied by the spheres, (ii) the volume VS of one sphere. (d) Empty the measuring cylinder and dry the spheres. Using the top-pan balance, measure and record (i) the mass mD of the small dish, (ii) the total mass mT of all 10 spheres and the dish. (e) Calculate the mass mS of one sphere. (f)

Calculate the density of the glass from which the spheres are made, given mS density = ––– . VS

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3 2

In this experiment, you will locate the position of the image of an object formed by a plane mirror. You have been provided with a plane mirror in a holder, three optical pins and a board. (a) Place page 4 of your answer booklet on the board provided. Place the plane mirror vertically in the middle of page 4 with the viewing surface facing towards the bottom of the page. Mark the position of the front surface of the mirror with a pencil. Extend this line across the whole width of the page and label it AB. Place an optical pin as an object towards the left hand side of the page and at a perpendicular distance of 8.0 cm from the pencil line. Label the position of the object as O. (b) Lower your head to the level of the bench and view the image of the object pin in the mirror. Move your head towards the right hand side of the page and place a second pin so that it hides the image of the object pin. Without moving your head, place a third pin in line with the second pin and the original image. Label the positions of these two pins as X and Y. Remove the pins and mirror and draw the line XY. Extend this line to meet the line AB. XY represents the reflected ray. The point where XY meets AB should be labelled M. Join M and O with a straight line. MO represents the incident ray. (c) Replace the mirror and the optical pin at O. Repeat the procedure described in (b) with your head in a different position. Locate and draw the path of a second reflected ray and a second incident ray. (d) Extend both reflected rays back through AB. Label the point where they meet as I.

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4 3

In this experiment, you will determine the resistance of the filament of a lamp for two values of the current through the filament. You have been provided with a power supply, a switch, a variable resistor, a lamp in a holder, a milliammeter, a voltmeter and connecting leads. (a) The circuit has already been set up by the Supervisor. On page 5 of your answer booklet, draw a diagram of the circuit. (b) Adjust the variable resistor until the current I through the lamp is about 40 mA. Record this current and the voltage V across the lamp. (c) Find the resistance R of the filament for this current using V R = –– .

I

(d) Repeat (b) for a current of about 50 mA. (i) Record the current and the corresponding voltage. (ii) Calculate the new value of the resistance of the filament. (e) Suggest why your values in (c) and (d)(ii) are different.

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5 Section B

4

In this experiment, you will investigate the cooling of a beaker of water. You have been provided with a 250 cm3 beaker, a thermometer, a stirrer, a supply of hot water and a stopwatch. (a) Hold the thermometer vertically in the clamp. Place the thermometer in the centre of the beaker with the bulb below the 200 cm3 mark, but not touching the sides or base of the beaker. The arrangement is shown in Fig. 4.1.

thermometer stand and clamp 200 cm3 mark

bench Fig. 4.1 (b) Record the temperature
R of the room. (c) Pour water from the hot water supply into the beaker until it reaches the 200 cm3 mark. (d) Take and record measurements of the variation with time t of the temperature
of the water, at suitable intervals, for a period of 8 minutes. Tabulate all your values of
and t. (e) Plot a graph of
/ °C (y-axis) against t / min (x-axis). (f)

Draw a smooth curve to fit the points on your graph. Determine the gradient of your graph at t = 4.0 minutes.

(g) At a particular time, the gradient represents the rate of fall of temperature and has a unit °C/min. P is the rate at which energy is lost from the water at this time and is given by P = m x c x (rate of fall of temperature) where m = mass of water = 0.2 kg and

c = specific heat capacity of water = 4200 J/(kg K).

Calculate P for the water at the time t = 4.0 minutes.

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