Paper 3 Nov 1999 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

4 NOVEMBER 1999

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.

This question paper consists of 5 printed pages, 3 blank pages and an inserted answer booklet.

SB (SLC / JB) QK94126/3 © UCLES 1999

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2 Section A Answer all the questions in this section.

1

In this experiment, you will determine the density of paper. Record your answers on page 2 of your Answer Booklet. (a) (i) (ii)

(b) (i)

Measure and record the length l and the width w of the sheet of paper labelled A. Using the top-pan balance, measure and record the mass m of the paper labelled A. You may fold the paper so that it fits easily on to the top-pan balance if you wish. In the stack of paper there are 100 sheets. Take and record measurements to determine the average thickness t s of the stack.

(ii) (c) (i)

Hence deduce the average thickness t of a single sheet of paper. Find the volume V of a single sheet given that V = l w t.

(ii)

Find the density of paper given that m density = — . V

(d) What assumption have you made in determining the density of paper?

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3 2

You are to form a magnified image of a piece of circuit board in order to determine an accurate value for the spacing of the holes in the board. Record your answers on page 3 of your Answer Booklet. (a) Set up the apparatus as shown in Fig. 2.1. Place the circuit board in front of and approximately 30 cm from the light source. Place the lens at a distance of approximately 20 cm from the circuit board. Adjust the position of the screen until a magnified real image is focused on the screen.

circuit board lens in holder

screen

light source

v

u

Fig. 2.1 (b) (i) (ii)

State whether the image formed on the screen is the right way up or inverted. Using the apparatus, how can you show which way up the image is?

(c) Adjust the position of the screen until it is 1.00 m away from the circuit board. Move the lens towards the circuit board until a sharp magnified image is formed on the screen. (d) Measure and record (i)

the distance u between the circuit board and the lens,

(ii)

the distance v between the lens and the screen.

(e) (i) (ii) (f)

Take and record measurements to determine the average spacing S between the centres of two adjacent holes on the image. Draw a diagram to explain how you made your determination of S.

Calculate (i)

the linear magnification m, given that

(ii)

v m = —, u the spacing s between the holes on the board, given that S s = —. m

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4 3

You are provided with a triangular lamina and are to determine the position of its centre of mass. Use pages 4 and 5 of your Answer Booklet. Refer to Fig. 3.1. nail A triangular card B plumbline

Fig. 3.1 (a) Suspend the triangular lamina from the small nail at the point labelled A. (b) Suspend the plumbline from the nail and mark the position of the plumbline on the lamina. (c) Repeat the procedure in (a) and (b) for the point labelled B. (d) (i) (ii)

Draw lines on the lamina representing the positions of the plumbline. Explain how you ensured that the positions of the lines were marked accurately.

(e) Label with X the intersection of the two lines. Measure and record the perpendicular distance p from X to the longest side of the triangle. (f)

How would you check that X is the centre of mass of the lamina?

(g) Tie your triangle loosely to your Answer Booklet as instructed on page 5.

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5 Section B

4

You are to investigate the electrical heating of some water in a beaker in order to find a value for the specific heat capacity of water. Use pages 5, 6 and 7 of your Answer Booklet for your answers. Do not switch on the circuit until you have completed (a) and (b). (a) Draw a diagram of the electrical circuit which has been set up for you. (b) Measure 50 cm3 of water and pour this into the beaker containing the heater. (c) Switch on the power supply and adjust the current I in the circuit to a value of 3.0 A. Measure and record I and the value of the potential difference V across the heater. Switch off the power supply. (d) Calculate the power P of the heater, given that P = I V. (e) Measure and record the initial temperature θi of the water in the beaker. (f)

Switch on the power supply and at the same time start the stopwatch. Measure the temperature θ and the time t at 30 second intervals for a period of 10 minutes. Tabulate your values of θ and t.

(g) Plot a graph of θ / °C (y-axis) against t /s (x-axis). (h) (i) (ii) (j)

Draw the best curved line through your points. Draw a tangent to the curve at time t = 0.

Determine the gradient of the tangent.

(k) Calculate a value for the specific heat capacity c of water given that P , c = –—– mG where and

m = mass of water used = 0.050 kg G = the gradient you have determined in (j) with unit °C/s.

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