Cambridge IGCSE Physics 0625 — 2019 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will investigate a pendulum. Carry out the following instructions, referring to Fig. 1.1 and Fig. 1.2. clamp clamp d bob one complete oscillation Fig. 1.1 Fig. 1.2 A pendulum has been set up for you as shown in Fig. 1.1. (a) • Adjust the length of the pendulum until the distance d measured to the centre of the bob is 50.0 cm. • Displace the bob slightly and release it so that it swings. Fig. 1.2 shows one complete oscillation of the pendulum. • Measure, and record in Table 1.1, the time t for 20 complete oscillations. • Calculate, and record in Table 1.1, the period T of the pendulum. The period is the time for one complete oscillation. • Calculate T 2. Record its value in Table 1.1. • Repeat the procedure using d = 60.0 cm, 70.0 cm, 80.0 cm and 100.0 cm. Table 1.1 d / cm t / s T / s T 2 / s2 50.0 60.0 70.0 80.0 100.0 [4] (b) Plot a graph of T 2 / s2 (y-axis) against d / cm (x-axis). You do not need to start your axes at the origin (0,0). [4] (c) Determine the gradient G of the line. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [1] 0.395(d) Calculate the acceleration of free fall g in m / s2 using the equation g = , where G is your G gradient from (c). Write down the value of g to a suitable number of significant figures for this experiment. g = .................................................m / s2 [2] [Total: 11]

Mark scheme: 1(a) table: t values increasing 1 T values = t / 20 1 T50 = 1.4 ± 0.1 (s) 1 T2 correct 1 1(b) graph: axes correctly labelled and right way round 1 suitable scales 1 all plots correct to ½ small square 1 good line judgement, thin, continuous line 1 1(c) triangle method indicated on graph 1 1(d) correct calculation of g 1 to 2 or 3 significant figures 1

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2 In this experiment, you will determine the resistance of a resistance wire. Carry out the following instructions, referring to Fig. 2.1. power supply A resistance wire l P sliding contact C metre rule V Fig. 2.1 (a) (i) Close switch. Measure and record the current I in the circuit. I = ......................................................... [2] (ii) • Place the sliding contact C at a distance l = 20.0 cm from P. • Measure, and record in Table 2.1, the potential difference V across the length l of the resistance wire. • Calculate, and record in Table 2.1, the resistance R of 20.0 cm of the resistance V wire. Use the equation R = . I • Repeat the procedure using l values of 40.0 cm, 60.0 cm, 80.0 cm and 100.0 cm. • Open switch. Table 2.1 l / cm V / V R / Ω 20.0 40.0 60.0 80.0 100.0 [4] (b) Look carefully at the values of l and R in Table 2.1. (i) Tick one box to show your conclusion from the results. R is constant within the limits of experimental accuracy. R is directly proportional to l within the limits of experimental accuracy. R decreases as l increases. There is no simple relationship between R and l. [1] (ii) Justify your conclusion by reference to your results. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (c) (i) Use the values in Table 2.1 to estimate the potential difference Ve across 50.0 cm of the resistance wire. Ve = ......................................................... [1] Ve (ii) Calculate the resistance of 50.0 cm of the resistance wire using the equation R = . I Use the value of current I from part (a). Give your answer to a suitable number of significant figures for this experiment and include the unit. R = ......................................................... [2] [Total: 11]

Mark scheme: 2(a)(i) 1 with correct unit 1 2(a)(ii) table: V values < 4 V 1 V values increasing 1 V values consistent to either 1 or 2 decimal places 1 R correct 1 2(b)(i) one box ticked, matching results 1 2(b)(ii) justification to match (i) 1 2(c)(i) value approximately halfway between 40 cm and 60 cm values 1 2(c)(ii) correct R value 1 2 or 3 significant figures with unit 1

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3 In this experiment, you will determine the focal length f of a lens. Carry out the following instructions referring to Fig. 3.1. D illuminated object u v screen lens bench Fig. 3.1 (a) • Place the screen a distance D = 80.0 cm from the illuminated object. • Place the lens between the object and the screen so that the lens is very close to the screen. • Move the lens slowly away from the screen until a clearly focused image is formed on the screen. (i) Measure, and record in Table 3.1, the distance u between the centre of the lens and the illuminated object. [1] (ii) Measure, and record in Table 3.1, the distance v between the centre of the lens and the screen. [1] (iii) Calculate, and record in Table 3.1, the focal length f of the lens using the equation uv f = . [1] D (b) Keep the screen at the distance D = 80.0 cm from the illuminated object. • Move the lens slowly away from the screen. The image will go out of focus. • Continue to move the lens slowly further away from the screen until another clearly focused (and now magnified) image is formed on the screen. • Measure, and record in Table 3.1, the distance u between the centre of the lens and the illuminated object. • Measure, and record in Table 3.1, the distance v between the centre of the lens and the screen. • Calculate, and record in Table 3.1, the focal length f of the lens using the equation uv f = . D [2] Table 3.1 u / cm v / cm f / cm (c) Calculate the average value fA of the focal length of the lens. Give your answer to a suitable number of significant figures for this experiment. fA = ................................................... cm [2] (d) State one precaution that you would take to obtain accurate readings in this experiment. ................................................................................................................................................... ............................................................................................................................................. [1] (e) Another student wants to obtain more measurements for u and for v to check the value for the focal length f of this lens. The student moves the screen a distance of 40.0 cm to the right. (i) Calculate the new value for the distance D between the illuminated object and the screen. D = ................................................... cm [1] (ii) The student moves the lens to a new position which is a distance from the object u = 22.2 cm. He observes the image on the screen and says it is clearly focussed at a distance v = 97.9 cm. uv Calculate the new value of the focal length f of the lens using f = . D f = ................................................... cm [1] (iii) State and explain briefly whether the values for fA and f in (e)(ii) are the same within the limits of experimental accuracy. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 3(a)(i) u = 55–65 (cm) 1 3(a)(ii) v = 80 − u (± 2 cm) 1 3(a)(iii) correct calculation of f 1 3(b) u = 15–25 (cm) and v = 80 − u (± 2 cm) 1 u and v values in table all in cm to the nearest mm 1 3(c) correct average 1 2 or 3 significant figures 1 3(d) one from: darkened room / brighter lamp object and lens at same height (above bench) object and lens and screen perpendicular to the bench ruler on bench or clamped mark centre of lens on holder move lens slowly / back and forth (to obtain best image) 1 3(e)(i) D = 120(.0) (cm) 1 3(e)(ii) f = 18.1 (cm) 1 3(e)(iii) Statement matches results (expect NO) justification to include the explanation of within / beyond the limits of experimental accuracy 1

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4 A student investigates the time taken for ice cubes in a container to melt using different insulating materials on the container. The following apparatus is available: a copper container a variety of insulating materials that can be wrapped around the copper container a thermometer a stopwatch a supply of ice cubes The student can also use other apparatus and materials that are usually available in a school laboratory. Plan an experiment to investigate the time taken for ice cubes to melt using different insulating materials. You are not required to carry out this investigation. In your plan, you should: • draw a diagram of the apparatus used • explain briefly how you would carry out the investigation • state the key variables that you would control • draw a table, or tables, with column headings, to show how you would display your readings (you are not required to enter any readings in the table) • explain how you would use your readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7] [Total: 7]

Mark scheme: 4 MP1 method diagram showing container, ice cubes, (thermometer and insulation) 1 MP2 method ice (in container), measure time (for all the ice) to melt 1 MP3 repeat with different insulators 1 MP4 control variables (total) mass / volume of ice cubes 1 MP5 control variables any one from: thickness / amount of insulation room temperature / other environmental condition size / shape / surface area of ice cubes initial temperature of ice cubes 1 MP6 table table with headings of (named) insulator and time with correct units 1 MP7 conclusion (use the table to) compare the insulator with the time taken for the ice to melt 1

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