Paper 3 Jun 1999 Physics

Answer guide for O Level Physics (5054/3) – Paper 3 Practical Test June 1999

1(a)

(c)

(d)

Mass of 20 spheres = mS - mP Mass of one sphere = (Mass of 20 spheres)/20 e.g. mS = 35.2 g, mP = 34.5 g, Mass of 20 spheres = 35.2 – 34.5 = 0.7 g hence m = 0.7/20 = 0.035 g. 1 A larger mass measurement, smaller percentage uncertainty in its value using all 20 spheres gives the average mass of a single sphere. 1 12 or more spheres in the groove and d calculated correctly, e.g. if 12 spheres (N) were used and they occupied a total length (L) of 36 mm, then; d = L/N = 36/12 = 3.0 mm. 1 Density calculated correctly using density = (6 m)/(π d3) e.g. Density = (6 x 0.035)/(π 0.33) = 2.5 g/cm3 (2 or 3 s.f.)

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2(a)

mW = 100 cm3 x 1 g/cm3 = 100 g.

1

(b) & (c)

Accurate interpolation between divisions on thermometer with correct units. Typical results; θ1 = 21.5 °C, θ2 = 28.8 °C

1

(d)

Q = mWcW(θ2 - θ1) = 0.100 x 4200 x (28.8 – 21.5) = 3066 J

1

(e) & (f)

Typical results; Mass of screw = 6.4 g = 0.0064 kg. T = Q/(mScS) = 3066/(0.0064 x 420) = 1141 ˚ Temperature of the Bunsen flame = T + θ2 = 1141 + 29 = 1170 °C

1

(g)

Sources of error in the experiment are mainly connected with heat loss e.g. heat conducted through the tongs, heat lost to the air when transferring the screw to the beaker, heat gained by the beaker as 1 well as the water.

3(a) (b)

Light is reflected from the back or silvered surface of the mirror. Normal drawn correctly, perpendicular to the line ABC at the point B. Angle of incidence correctly drawn as 35° Initial angle of reflection and position of the line XY correct on the diagram. Position of new reflected ray judged to be correct by eye. Correct value 50°. A value between 47° and 53° is acceptable.

(c) & (d) (e) (f)

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Answer guide for O Level Physics (5054/3) – Paper 3 Practical Test June 1999

4(a), (b) & Check that the metre rule is vertical either by aligning it with a vertical door or window frame / by using a set square against a (c) horizontal bench. Candidates should state how parallax is avoided i.e. by keeping the eye level with the bottom of the length of rubber or by using a set square against the vertical rule h and h0 recorded to the nearest mm and e found by subtraction. (d)

(e)

(f)

(g)

(h)

Results tabulated with quantities and units in the headings of the table including values of h, e and W. All W values should be in newtons e.g. a mass of 50 g (= 0.050 kg) has a weight W of 0.5 N. This experiment should produce a curve whose gradient is increasing with increasing force. Six points within 2 mm of curve 1 mark, eight points 2 marks. The axes of the graph labelled with the appropriate quantity and units e.g. extension/mm and force/N. The scale not based on 3, 7, 11 etc. Data plotted fills more than half the page in either direction. Points plotted carefully with smooth neat curve drawn. The extension when the plasticene is suspended from the paper clip should be determined. The line on the graph should then be used to determine the corresponding weight WP of plasticene.

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1

1

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Supervisors provided a mass of 55 g of plasticene. This would have a weight of 0.54 N. Weight in the range 0.49 N to 0.59 N 1 When the plasticene is fully immersed in water the extension of the length of rubber should reduce, leading to a weight of approximately 1 0.25 N. A value in the range 0.20 N to 0.30 N gains a mark for accuracy. 1 Density = kWP/(WP – WW) = 1.00 x 0.54 / (0.54 – 0.25) = 1.86 g/ cm3 quoted to 2 or 3 s.f. with units g/cm3

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