Cambridge IGCSE Physics 0625 — 2017 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will compare the oscillations of two pendulums. Carry out the following instructions, referring to Figs. 1.1 and 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. This pendulum has a spherical pendulum bob. (a) Adjust the pendulum until the distance d measured to the bottom of the bob is 50.0 cm. Explain briefly how to use the set-square to avoid a parallax (line of sight) error when measuring the distance d. You may draw a diagram. ................................................................................................................................................... ...............................................................................................................................................[1] (b) Move the bob slightly to the side and release it so that it swings. Fig. 1.2 shows one complete oscillation of the pendulum. (i) Measure the time t1 for 20 complete oscillations. t1 = ...........................................................[1] (ii) Calculate the period T1 of the pendulum. The period is the time for one complete oscillation. T1 = ...........................................................[2] (c) Remove the pendulum from the clamp and attach the second pendulum provided to the clamp. This has a long, thin bob. Adjust the pendulum until the distance d measured to the bottom of the bob is 50.0 cm. Displace the bob slightly and release it so that it swings. (i) Measure the time t2 for 20 complete oscillations. t2 = ...........................................................[1] (ii) Calculate the period T2 of the pendulum. T2 = ...........................................................[1] (d) A student suggests that the periods T1 and T2 should be equal. State whether your results support this suggestion. Justify your answer by reference to the results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ...............................................................................................................................................[2] (e) The period T of a pendulum can be determined by measuring the time t for 20 complete oscillations and then calculating the period. Some students are asked to explain the reason for this method being more accurate than measuring the time taken for one oscillation. Tick the box next to the sentence that gives the best explanation. The method eliminates errors from the measurements. The method is more accurate because the experiment is repeated. The method includes more readings so there is less chance for errors. The method reduces the effect of errors when starting and stopping the stopwatch. [1] (f) A student plans to carry out more pendulum experiments. He considers possible variables, and precautions to improve accuracy. In the following list, mark the possible variables with the letter V and the precautions with the letter P. amplitude of swing length of pendulum mass of pendulum bob shape of pendulum bob use of a reference point to aid counting viewing the rule at right angles when measuring the length [2] [Total: 11]

Mark scheme: 1(a) correct use of set-square AND vertical ruler 1 1(b)(i) t1 = 29.5 ± 2.5 (s) 1 1(b)(ii) correct T1 from candidate’s value of t1 1 unit s seen at least once in (i) or (ii) 1 1(c)(i) t2 = 27.7 ± 2.5 (s) 1 1(c)(ii) T2 < T1 and to 2 or 3 significant figures 1 1(d) statement to match readings 1 justification to include the idea of within (or beyond e.c.f) the limits of experimental accuracy e.g. (very) close / almost equal / the same 1 1(e) final box ticked 1 1(f) 4 or 5 correct (fewer than 4 correct = 0 marks) 1 From top box to bottom box V, V, V, V, P, P all correct (= full marks) 1

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2 In this experiment, you will investigate the cooling of water. (a) Measure room temperature θR. θR = ...........................................................[1] (b) • Pour 50 cm3 of the hot water provided into beaker A. • Measure the temperature θH of the water in beaker A. θH = ............................................................... • Add 50 cm3 of the cold water provided to the hot water in beaker A. Stir the water briefly. • Measure the temperature θM of the water in beaker A. θM = ............................................................... • Calculate the temperature fall θF using the equation θF = θH − θM. θF = ............................................................... • Empty beaker A. [3] (c) Suggest one reason for stirring the water before reading θM. ................................................................................................................................................... ...............................................................................................................................................[1] (d) Repeat the procedure in (b) using 75 cm3 of hot water and 75 cm3 of cold water. θH = ............................................................... θM = ............................................................... θF = ............................................................... [1] (e) Repeat the procedure in (b) using 100 cm3 of hot water and 100 cm3 of cold water. θH = ............................................................... θM = ............................................................... θF = ............................................................... [1] (f) Measure room temperature θR again. θR = ............................................................... Complete the appropriate sentence. • Room temperature has remained constant at ............... . • Room temperature has decreased by ............... . • Room temperature has increased by ............... . [1] (g) A student states that the temperature fall θF should be the same each time because the proportions of hot and cold water are the same. Suggest a reason why θF could be very different in (b), (d) and (e). ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] (h) Suggest an improvement to the apparatus to make it more likely that θF would be the same each time. ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] (i) Suggest a condition, not included in your answer to (h), that could be controlled to make it more likely that θF would be the same each time. ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 11]

Mark scheme: 2(a) realistic room temperature 1 2(b) realistic hot water temperature 1 mixture temperature between hot and room 1 temperature fall correct AND °C seen at least once and not contradicted 1 2(c) to make sure that the temperature is the same throughout 1 2(d) realistic new temperatures 1 2(e) realistic new temperatures 1 2(f) room temperature seen and correct conclusion 1 2(g) heat loss (to surroundings) / time delays in transferring the water or did not wait for thermometer readings to stabilise 1 2(h) insulation 1 2(i) same starting temperature / same room temperature 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. u v screen lens bench illuminated object Fig. 3.1 (a) (i) Place the screen 100 cm from the illuminated object. • Place the lens between the object and the screen so that the centre of the lens is at a distance u = 20.0 cm from the object. • Adjust the position of the screen until a clearly focused image is formed on the screen. • Measure the distance v between the centre of the lens and the screen. Record the values of u and v in Table 3.1. Table 3.1 u / cm v / cm (ii) Repeat the procedure using values for u of 22.0 cm, 25.0 cm, 30.0 cm and 35.0 cm. [3] (b) Plot a graph of v / cm (y-axis) against u / cm (x-axis). You do not need to start your axes at the origin (0, 0). Draw the best-fit curve. [4] (c) (i) • Mark, with a cross, the point on the graph grid where u = 25.0 cm and v = 25.0 cm. • Mark, with a cross, the point on the graph grid where u = 35.0 cm and v = 35.0 cm. • Join these two points with a straight line. [1] (ii) • Record u1, the value of u at the point where the straight line crosses your graph line. u1 = ..........................................................cm • Record v1, the value of v at the point where the straight line crosses your graph line. v1 = ..........................................................cm [1] (u1 + v1) (iii) Calculate the focal length f of the lens using the equation f = . 4 f = ..........................................................cm [2] [Total: 11]

Mark scheme: 3(a)(i),(ii) correct u values 20(.0), 22(.0), 25(.0), 30(.0), 35(.0) 1 v values decreasing and all > 22.0 cm 1 consistent 2 or consistent 3 significant figures for v 1 3(b) graph: axes correctly labelled and not reversed 1 suitable scales 1 all plots correct to ½ small square 1 good best-fit curve judgement, thin, continuous line 1 3(c)(i) 2 points and straight line correct 1 3(c)(ii) u1 and v1 read correctly to ½ small square 1 3(c)(iii) correct calculation of f from candidate’s values 1 f value rounding to 14–16 cm 1

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4 A student has a selection of rubber bands of different thicknesses. He is investigating the amount of stretch produced by different loads. Fig. 4.1 shows the set-up used. clamp boss stand rubber band bench hook Fig. 4.1 In addition to the apparatus shown in Fig. 4.1, the following apparatus is available to the student: metre rule selection of different rubber bands selection of loads. Plan an experiment to investigate how rubber bands of different thicknesses stretch when loaded. You are not required to carry out this experiment. You should • 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 briefly how you would use your readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[7] [Total: 7]

Mark scheme: 4 method: MP1 measure length of band 1 MP2 hang load, measure new length 1 MP3 repeat with different thicknesses/widths 1 control variable: MP4 use same (original) length of band each time 1 table: MP5 table with columns for thickness, (load) and length / extension with units 1 conclusion: MP6 plot a graph of extension / length against thickness (for the same load) OR load against extension / length for different thicknesses OR comparison via a table e.g. compare extensions / lengths of different thicknesses for the same load 1 one additional point: MP7 use same load / same range of loads use at least 5 thicknesses / take at least 5 different readings to plot a graph show how to measure extension e.g. l – l0 use same type / material of rubber band 1

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