Cambridge International AS Level Physics Answers to self-assessment questions Answers to SAQs Chapter P1 13 h / cm 2 2 d / cm d / cm 1.0 18.0 324 1Probably 50 Ω, 100 Ω, 200 Ω, 300 Ω, 400 Ω, 500 Ω. They cover the whole range with roughly equal differences. 2.5 28.4 807 4.0 35.8 1280 5.5 41.6 1730 2a 7.0 47.3 2240 9.0 53.6 2870 b 14 a d2 / cm2 3000 + + 2000 3Left-hand diagram indicates systematic error. Right-hand diagram indicates random error. 4Pointer does not indicate zero when load = 0; scale incorrectly calibrated. 51 mm at either end = ±2 mm; but if several measurements are required end-to-end and the tape measure is not long enough, this will increase the uncertainty. This assumes the tape measure is drawn tightly but does not stretch in length. 6±0.5 °C or ±1.0 °C 7Between ±0.2 cm and ±1 cm. 8Between ±0.2 s and ±0.5 s. 9 a b c d Average = (20.6 + 20.8)/2 = 20.7 ± 0.1 Average = (20 + 30 + 36)/3 = 29 ± 8 Average = (0.6 + 1.0 + 0.8 + 1.2)/4 = 0.9 ± 0.3 Average = (20.5 + 20.5)/2 = 20.5 ± 0.1 10 ±0.8% 11 a ±5.7% or 6% b The pendulum is moving during measurement. + 1000 0 + + 0 2 4 6 h / cm 8 10 b Gradient = 320 cm; y-intercept = 0 cm2 approx. 15 If T is proportional to m, then T = km. 6.3 Two values of k are 4.6 0.9 = 5.1 and 1.2 = 5.25. The % difference in the k values is 0.15 × 100 = 2.9%. 5.1 The percentage difference in the T value is 0.2 × 100 = 4.3%. 4.6 The criterion is that the % difference in the k values should be less than the % difference in the raw data for proportionality to be shown. This has been shown, so the data is consistent with a proportional relationship. 2 16 Two values of k = tr are 3.41 and 3.0. They differ by about 14%. The percentage uncertainty in r is 3%. Since the % uncertainty in the k values is larger than the % uncertainty in the readings, the data is not consistent with a proportional relationship. 12 ±0.25 V Cambridge International AS and A Level Physics © Cambridge University Press 2014