Paper 3 May 1999 Physics

UNIVERSITY OF CAMBRIDGE LOCAL EXAMINATIONS SYNDICATE General Certificate of Education Ordinary Level

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PHYSICS PAPER 3 Practical Test Monday

21 JUNE 1999

Morning

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. Any additional sheets should be attached firmly to the answer booklet.

This question paper consists of 6 printed pages, 2 blank pages and an inserted answer booklet. SB (KG/JB) QF92360/2 © 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 the glass from which some spheres are made. Record your answers on page 2 of your Answer Booklet. (a) (i)

Using the top pan balance, measure and record 1. the mass mp of the empty petri dish, 2. the mass ms of the petri dish and 20 spheres.

(ii)

Hence determine the average mass m of a single sphere.

(b) Explain why you were instructed to use 20 spheres rather than a single sphere. (c) Place a number of spheres into the groove in the block of wood. (i)

Record the number N of spheres used.

(ii)

Make sure that the spheres are touching. Measure and record the total length L occupied by the spheres.

(iii)

Determine the mean diameter d of a sphere, given that L d = –– . N

(d) Find the density of glass, given that 6m density = ––– . πd 3

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3 2

You are to estimate the temperature of the flame of a Bunsen burner by applying the law of conservation of energy when a screw, heated in the flame, is plunged into a beaker of water. Record your answers on page 3 of your Answer Booklet. (a) Measure 100 cm3 of water and pour it into the beaker labelled A. Given that 1 cm3 of water has a mass of 1 g, record the mass mw of water in the beaker. (b) Measure and record the temperature θ1 of this water. (c) Adjust the air supply to the Bunsen burner to create the roaring flame. Using the tongs, hold the screw in the hottest part of the flame. After approximately 1 minute, transfer the screw to the beaker of water. Measure and record the final temperature θ2 of the water. (d) Determine the energy Q gained by the water, given that Q = mwcw(θ2 – θ1), where cw = specific heat capacity of water = 4200 J/(kg K). (e) The screw loses the same amount of energy Q as determined in (d). Find the fall in temperature T of the screw given that Q T = ––––– , mscs where ms = mass of the screw which is given on the card and (f)

cs = specific heat capacity of the material of the screw = 420 J/(kg K).

Use your answers to estimate the temperature of the flame of a Bunsen burner.

(g) Suggest one source of error in this experiment.

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4 3

You are to measure the angle through which a reflected ray is turned when a mirror is rotated through an angle of 25°. Use page 4 of your Answer Booklet. (a) From which surface of the mirror is most of the light reflected? (b) On page 4 of the Answer Booklet, the line ABC will represent the position of the reflecting surface of the mirror. (i)

Draw a normal to the line AC at B in the direction of the bottom of the page.

(ii)

Draw a line through B to represent a ray with an angle of incidence of 35°.

(c) (i)

Place your Answer Booklet on the soft-board and place the reflecting surface of the mirror along ABC.

(ii)

Place two pins vertically on the line marking the position of the incident ray. Look from the opposite side of the normal and place two pins in line with the images of the first two pins. These pins mark the path of the reflected ray.

(iii)

Remove the mirror and pins, and draw in the path of the reflected ray.

(d) Draw a line XY through B at an angle of 25° to ABC, as shown in Fig. 3.1. Y B

A

25°

C

X Fig. 3.1 (e) Place the reflecting surface of the mirror along the line XY and place two pins on the line of the original incident ray. Look at the mirror again and place two further pins in line with the images of the pins on the incident ray. These pins mark the new path of the reflected ray. Remove the mirror and pins, and draw in the path of the new reflected ray. (f)

Measure and record the angle between the two paths of the reflected ray.

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5 Section B 4

You are to use a length of rubber as a force meter. You are to weigh a block of plasticine in air and in water to determine a value for the density of plasticine. Use pages 5 to 7 of your Answer Booklet. The length of rubber is hanging vertically, as shown in Fig. 4.1.

paper clip

rubber

stand

paper clip

Fig. 4.1 (a) (i)

Using the second stand and clamp, set the metre rule vertically, close to the length of rubber, with the zero end of the rule on the bench.

(ii) Measure and record the height ho (in mm) of the bottom of the length of rubber above the bench. (b) Explain (i)

how you ensured that the metre rule was vertical,

(ii)

any special precautions taken to ensure that ho was measured accurately.

(c) (i)

Hang a 10 g mass hanger (which corresponds to a weight W of 0.1 N) from the paper clip at the bottom of the rubber.

(ii)

Measure and record the new height h (in mm) of the bottom of the rubber above the bench.

(iii)

Calculate (ho – h) which is the extension e of the rubber.

(d) (i) (ii)

Repeat (c) for a range of values of W up to 0.8 N. Tabulate all your measurements of h, including those in (c). Include in your table the corresponding values of e and W.

(e) Plot a graph of e/mm (y-axis) against W/N (x-axis). (f)

(i)

Replace the masses suspended from the rubber with the plasticine block. Determine the extension ep due to the plasticine.

(ii)

Use your graph to find the corresponding weight Wp. Record this weight.

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6 (g) (i)

Place the beaker of water underneath the suspended plasticine block, as shown in Fig. 4.2. Raise the beaker of water until the block is fully submerged but not touching the beaker, as shown in Fig. 4.3.

plasticine block beaker held in position whilst reading taken

beaker

Fig. 4.2

Fig. 4.3

(ii)

Determine the corresponding extension ew of the rubber when the plasticine is fully submerged in the water.

(iii)

Use your graph to find the corresponding weight Ww. Record this weight.

(h) Calculate the density of plasticine, given that k Wp density = ––––––– , Wp – Ww 3 where k = 1.00 g/cm .

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