Cambridge IGCSE Physics 0625 — 2018 May/June Paper 5 · Variant 1

1 In this experiment, you will determine the acceleration of free fall g using a pendulum. Carry out the following instructions, referring to Fig. 1.1 and Fig. 1.2. clamp clamp d one complete bob 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. (i) Measure the time t for 10 complete oscillations. t = .......................................................... [1] (ii) Calculate the period T of the pendulum. The period is the time for one complete oscillation. T = .......................................................... [1] (iii) Calculate T 2. T 2 = .......................................................... [2] 20 (iv) Calculate the acceleration of free fall g using the equation g = 2. T g = .......................................................... [1] (b) Adjust the pendulum until the distance d measured to the centre of the bob is 100.0 cm. (i) Repeat the procedure in (a)(i), (a)(ii) and (a)(iii). t = ............................................................... T = ............................................................... T 2 = ............................................................... [1] 40 (ii) Calculate the acceleration of free fall g using the equation g = 2. T g = ............................................................... [2] (c) A student states that repeating the experiment improves the reliability of the value obtained for g. Suggest two changes that you would make to improve the reliability. The stopwatch cannot be changed. 1. ............................................................................................................................................ ............................................................................................................................................ 2. ............................................................................................................................................ ............................................................................................................................................ [2] (d) State one precaution that you took in this experiment in order to obtain accurate readings. ................................................................................................................................................... ...............................................................................................................................................[1] [Total: 11]

Mark scheme: 1(a)(i) t = 13 to 15 (s) 1 1(a)(ii) T = t / 10 (s) 1 1(a)(iii) T2 correct 1 Unit s2 1 1(a)(iv) g correct calculation from T2 1 1(b)(i) New set of values present with t value greater than (a)(i) 1 1(b)(ii) g in range 8 to 12(m / s2) 1 both g (1(a)(iv) and 1(b)(ii)) values 9 to 11(m / s2) 1 1(c) Use of additional d values OR use a larger d value 1 Count more swings 1 1(d) Any one from: Perpendicular viewing of rule Counting beginning with zero (owtte) Use of fiducial mark (owtte) Use of set-square or horizontal rule to aid measurement of d Use rule close to/touching the rule Time taken from centre of swing, (not extremities) 1

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2 In this experiment, you will investigate resistance. The circuit shown in Fig. 2.1 has been set up for you. power supply A R1 R2 R3 V Fig. 2.1 (a) (i) Switch on. Measure and record the potential difference V1 across the resistor R1 and the current I in the circuit. Switch off. V1 = ............................................................... I = ............................................................... [2] V1 (ii) Calculate the resistance of the resistor R1 using the equation R1 = . I R1 = .......................................................... [1] (b) Disconnect the voltmeter. Connect the voltmeter across the resistor R2. Switch on. (i) Measure and record the potential difference V2 across the resistor R2. Switch off. V2 = ............................................................... V2 (ii) Calculate the resistance of the resistor R2 using the equation R2 = . I R2 = .......................................................... [1] (c) Disconnect the voltmeter. Connect the voltmeter across the resistor R3. Switch on. (i) Measure and record the potential difference V3 across the resistor R3. Switch off. V3 = ............................................................... V3 (ii) Calculate the resistance of the resistor R3 using the equation R3 = . I R3 = .......................................................... [1] (iii) Calculate the resistance R of resistors R1, R2 and R3 connected in series, using the equation R = R1 + R2 + R3. Give your answer to a suitable number of significant figures for this experiment. R = .......................................................... [1] (d) State whether your results suggest that the three resistors have the same value of resistance. Justify your statement by reference to your results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] (e) Complete the circuit diagram in Fig. 2.2 to show: • the three resistors connected in parallel • the voltmeter connected to measure the potential difference across the resistors • a variable resistor connected to control the current in all three resistors. You are not required to set up this circuit. power supply A Fig. 2.2 [3] [Total: 11]

Mark scheme: 2(a)(i) V1 to at least 1 dp and < 4 V 1 I to at least 2 dp and < 1 A 1 2(a)(ii) Correct calculation of R1 1 2(b)(i),(ii) R2 present within 10% of R1 1 2(c)(i),(ii) R3 present and V, A, Ω at least once and not contradicted 1 2(c)(iii) R correct and to 2 or 3 significant figures 1 2(d) Statement matches readings (Expect YES) 1 Justification to include the idea of within the limits of experimental accuracy (but accept beyond limits, if ecf allowed for statement matching readings) 1 2(e) 3 resistors in parallel 1 Correct variable resistor symbol 1 Other symbols and circuit correct 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. illuminated object u v screen lens Fig. 3.1 (a) • Place the screen a distance D = 70.0 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. • Measure, and record in the table, the distance v between the centre of the lens and the screen. (ii) Calculate the product uv. Record your answer in the table. (iii) Repeat the procedure using values for D of 75.0 cm, 80.0 cm, 85.0 cm and 90.0 cm. Table 3.1 D / cm u / cm v / cm uv / cm2 70.0 75.0 80.0 85.0 90.0 [3] (b) Plot a graph of uv / cm2 (y-axis) against D / cm (x-axis). You do not need to start your axes at the origin (0,0). [4] (c) The focal length f of the lens is numerically equal to the gradient of the line. Determine the gradient G of the line. Show clearly on the graph how you obtained the necessary information. G = ...........................................................[2] (d) Suggest two difficulties in this experiment when trying to obtain accurate readings. 1. ............................................................................................................................................ ............................................................................................................................................ 2. ............................................................................................................................................ ............................................................................................................................................ [2] [Total: 11]

Mark scheme: 3(a) Table: First u 45 to 51 (cm) and first v 19 to 25 1 u values > v values 1 uv values correct 1 3(b) Graph: Axes correctly labelled and right way round 1 Suitable scales 1 All plots correct to ½ small square 1 Good line judgement, single, thin, continuous line 1 3(c) Triangle method clearly shown on graph 1 Triangle using at least half of candidate’s line 1 3(d) Any two from: Finding exact position that gives clearest image Measuring to centre of lens Room too bright/lamp too dim 2

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4 A student is investigating the effect of double-walled insulation on the rate of cooling of hot water in a copper container. The student places the copper container inside a larger metal container. He is investigating the effect of the size of the air gap between the copper container and larger metal containers. Plan an experiment to investigate the effect of the size of the air gap between the copper container and larger metal containers on the rate of cooling of hot water. The following apparatus is available: a copper container a number of metal containers of different diameters (all larger than the copper container) a thermometer a stopwatch a measuring cylinder a supply of hot water. You can also use other apparatus and materials that are usually available in a school laboratory. You are not required to carry out this investigation. In your plan, 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 how you would use your readings to reach a conclusion. You may draw a diagram if it helps your explanation. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... ......................................................................................................................................................[7] [Total: 7]

Mark scheme: 4 Method to include: Hot water in copper can, time taken for temperature to drop 1 Correct use of at least 3 larger outer containers, separately 1 Some indication that size of air gap is measured 1 Any two from: Use of something to cover air gap Use of lid on copper can Same starting temperature Same room temperature Same volume of hot water Use of ‘control’ with no outer container Inner container standing on an insulator Uniform air gap all round 2 Table with clear columns for temperature and / or time (to match method) and air-gap, with appropriate units 1 Conclusion: Least temperature drop OR longest time for temperature to drop shows lowest cooling rate OR best insulation OR plot temperature against time and least gradient shows lowest cooling rate (ora) 1 NOTE: The principle to apply here is ‘could I draw a significantly better line, using these points, under examination conditions?’ If the answer is definitely ‘yes’, do not award the mark. NOTE: – If candidate’s scale consists of actual readings at equal intervals this will produce a perfect straight line! The only marks available in this case are the first (axes right way round and labelled) So maximum 1. – If axes are wrong way round, the other 3 marks are still available.

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