Cambridge IGCSE Physics Laboratory Practical Book Answer

Answers to Cambridge IGCSE ® Physics Laboratory Practical Book Experimental skills and abilities Skills for scientific enquiry 1 (a) measuring cylinder (g) voltmeter (b) digital balance (h) digital timer (c) metre rule (i) protractor (d) micrometer screw gauge (j) ammeter (e) liquid in glass thermometer (k) ruler (f) stopwatch 2 (a) Measure the thickness of at least 20 pages with a micrometer screw gauge and divide the value by 20 to obtain the average thickness of one page. (b) Time at least 10 oscillations with a stopwatch and divide the result by 10 to obtain the average time for one oscillation. (c) Weigh at least 20 pins on a balance and divide the result by 20 to obtain the average mass of one pin. 3 Device Accuracy metre rule 1 mm vernier scale 0.1 mm micrometer screw gauge 0.01 mm stopwatch 0.5 s digital timer 1 ms digital balance typically 1 g or 0.1 g liquid in glass thermometer 1 °C 100 ml measuring cylinder 1 ml or 1 cm 3 4 (a) 9.75 (b) 9.8 (c) 1 × 10 1 5 (a) P = IV = 250 × 10 - 3 × 8.0 = 2.0 J/s P 60 (b) I = = = 5.0 A V 12 6 true current = (26 - 2) mA = 24 mA 7 (a) (i) speed, time (ii) mass, acceleration (iii) Manipulated (independent) variable Fixed variable Responding (dependent) variable time mass, acceleration speed 1 Cambridge IGCSE Physics Laboratory Practical Book © Heather Kennett 2015

Answers to Cambridge IGCSE ® Physics Laboratory Practical Book Experimental skills and abilities Skills for scientific enquiry 1 (a) measuring cylinder (g) voltmeter (b) digital balance (h) digital timer (c) metre rule (i) protractor (d) micrometer screw gauge (j) ammeter (e) liquid in glass thermometer (k) ruler (f) stopwatch 2 (a) Measure the thickness of at least 20 pages with a micrometer screw gauge and divide the value by 20 to obtain the average thickness of one page. (b) Time at least 10 oscillations with a stopwatch and divide the result by 10 to obtain the average time for one oscillation. (c) Weigh at least 20 pins on a balance and divide the result by 20 to obtain the average mass of one pin. 3 Device Accuracy metre rule 1 mm vernier scale 0.1 mm micrometer screw gauge 0.01 mm stopwatch 0.5 s digital timer 1 ms digital balance typically 1 g or 0.1 g liquid in glass thermometer 1 °C 100 ml measuring cylinder 1 ml or 1 cm 3 4 (a) 9.75 (b) 9.8 (c) 1 × 10 1 5 (a) P = IV = 250 × 10 - 3 × 8.0 = 2.0 J/s P 60 (b) I = = = 5.0 A V 12 6 true current = (26 - 2) mA = 24 mA 7 (a) (i) speed, time (ii) mass, acceleration (iii) Manipulated (independent) variable Fixed variable Responding (dependent) variable time mass, acceleration speed 1 Cambridge IGCSE Physics Laboratory Practical Book © Heather Kennett 2015

(b) 1.0 Answers 0.8 0.6 m/s / rise = (0.8 − 0.2) m / s = 0.6 m / s speed 0.4 0.2 run = (0.20 − 0.05) s = 0.15 s 0 0.05 0.10 0.15 0.20 0.25 0.30 time / s 0.6 m/s (c) gradient = = 4.0 m/s 2 0.15 s (d) Speed is proportional to time (duration) of fall. 2 Cambridge IGCSE Physics Laboratory Practical Book © Heather Kennett 2015

(b) 1.0 Answers 0.8 0.6 m/s / rise = (0.8 − 0.2) m / s = 0.6 m / s speed 0.4 0.2 run = (0.20 − 0.05) s = 0.15 s 0 0.05 0.10 0.15 0.20 0.25 0.30 time / s 0.6 m/s (c) gradient = = 4.0 m/s 2 0.15 s (d) Speed is proportional to time (duration) of fall. 2 Cambridge IGCSE Physics Laboratory Practical Book © Heather Kennett 2015

1 General physics Answers 1.1 Simple pendulum Variables Table 1 Manipulated (independent) Fixed Responding (dependent) length mass period mass length period Method The length of the pendulum was measured from the point of support to the centre of the bob with a metre rule. Timing ten oscillations, rather than one, improves the degree of accuracy of the measurement because the timing is over a longer period. For example, if the timing measurement is accurate to 0.5 s and the time measured is 2 s the degree of accuracy is 0.5 parts in 2 or 25 parts in 100. However, if the time measured is 20 s, the degree of accuracy is 0.5 parts in 20 or 2.5 parts in 100. Conclusions 1 The period of a simple pendulum increases when the length of the pendulum increases. 2 The period of a simple pendulum does not change when the mass of the pendulum changes. To summarise: the period of a simple pendulum varies with the length and not the mass of the pendulum. Evaluation Reliability of results could be improved by: • timing a greater number of oscillations • investigating a larger range of pendulum lengths and masses • determining the length of the pendulum more accurately (by measuring the diameter of the bob with vernier callipers). Extension g = 9.8 m/s 2 1.2 Density Method The dimensions of the blocks A and B were measured with: a ruler to an accuracy of 1 mm. The diameter of the wire C was measured: several times with a micrometer screw gauge to an accuracy of 0.01 mm. The diameter of the ball D can be obtained by setting it between two smooth vertical surfaces (blocks A and B could be used if they are as high as the ball’s diameter) and measuring the distance between the surfaces with a ruler . The volume of object E was obtained by: recording the water level in a measuring cylinder before and after it was submerged. Mass was measured with a balance of accuracy: e.g. 1 g . 3 Cambridge IGCSE Physics Laboratory Practical Book © Heather Kennett 2015

1 General physics Answers 1.1 Simple pendulum Variables Table 1 Manipulated (independent) Fixed Responding (dependent) length mass period mass length period Method The length of the pendulum was measured from the point of support to the centre of the bob with a metre rule. Timing ten oscillations, rather than one, improves the degree of accuracy of the measurement because the timing is over a longer period. For example, if the timing measurement is accurate to 0.5 s and the time measured is 2 s the degree of accuracy is 0.5 parts in 2 or 25 parts in 100. However, if the time measured is 20 s, the degree of accuracy is 0.5 parts in 20 or 2.5 parts in 100. Conclusions 1 The period of a simple pendulum increases when the length of the pendulum increases. 2 The period of a simple pendulum does not change when the mass of the pendulum changes. To summarise: the period of a simple pendulum varies with the length and not the mass of the pendulum. Evaluation Reliability of results could be improved by: • timing a greater number of oscillations • investigating a larger range of pendulum lengths and masses • determining the length of the pendulum more accurately (by measuring the diameter of the bob with vernier callipers). Extension g = 9.8 m/s 2 1.2 Density Method The dimensions of the blocks A and B were measured with: a ruler to an accuracy of 1 mm. The diameter of the wire C was measured: several times with a micrometer screw gauge to an accuracy of 0.01 mm. The diameter of the ball D can be obtained by setting it between two smooth vertical surfaces (blocks A and B could be used if they are as high as the ball’s diameter) and measuring the distance between the surfaces with a ruler . The volume of object E was obtained by: recording the water level in a measuring cylinder before and after it was submerged. Mass was measured with a balance of accuracy: e.g. 1 g . 3 Cambridge IGCSE Physics Laboratory Practical Book © Heather Kennett 2015