Cambridge IGCSE Physics 0625 — 2023 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will investigate the period of a pendulum. Complete 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) The distance d is measured from the bottom of the clamp to the centre of the bob. • Adjust the length of the pendulum until d = 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 10 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 and record the value in Table 1.1. • Write the unit for T 2 in the column heading. [3] Table 1.1 d / cm t / s T / s T 2 / 50.0 100.0 (b) Repeat the procedure in (a) using d = 100.0 cm. [3] (c) A student suggests that T 2 is directly proportional to d. Explain briefly how to test the suggestion using the results in Table 1.1. ................................................................................................................................................... ............................................................................................................................................. [2] (d) Describe how you measure the distance d as accurately as possible. Draw a diagram to help your explanation. ................................................................................................................................................... ............................................................................................................................................. [2] (e) Explain why timing 10 oscillations gives a more accurate result for the period T than timing one oscillation. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: Question Answer Marks 1(a) t = 12 – 16 and T = t / 10 1 T2 correct 1 s2 1 1(b) t = 19 – 21 1 T and T2 correct 1 T2 both given to same number of significant figures 1 1(c) calculate T2 / d (or reciprocal of this) 1 judge if (close enough to be considered) equal 1 OR compare the T2 and d values judge if the second value is (close enough to) double the first value OR plot a graph of T2 against d (if directly proportional) it will be a straight line passing through the origin 1(d) diagram to show (correct use of) a horizontal aid (e.g., a set-square / ruler) 1 matching wording 1 OR measure the diameter of the bob with two blocks and a ruler / micrometer divide by 2 to find the radius and add this on to the length of the string OR measure to the top and the bottom of the bob find the average 1(e) reduces the effect of (reaction) timing errors/reduces the percentage error / uncertainty 1 / the (reaction time) error is spread over 20 oscillations

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2 In this experiment, you will investigate the resistance of a wire. Complete the following instructions, referring to Fig. 2.1. A l B C resistance wire V sliding contact S Fig. 2.1 (a) Close the switch. Measure the current I in the circuit. I = ......................................... [1] (b) Place the sliding contact at a distance l = 10.0 cm from B. Measure, and record in Table 2.1, the potential difference (p.d.) V across the length l of resistance wire BC. Open the switch. Calculate, and record in Table 2.1, the resistance R of 10.0 cm of the resistance wire using the equation V R = I where I is the current recorded in (a). Close the switch. Repeat the procedure using l = 20.0 cm, 30.0 cm, 40.0 cm and 50.0 cm. Open the switch. Table 2.1 l / cm V / V R / Ω 10.0 20.0 30.0 40.0 50.0 [4] (c) Plot a graph of R / Ω (y-axis) against V / V (x-axis). Start both axes at the origin (0,0). Draw the best-fit line. 0 0 [4] (d) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ......................................................... [2] [Total: 11]

Mark scheme: 2(a) I < 1 A to at least 2 decimal places with unit 1 2(b) V values to at least 1 decimal place 1 V values increasing 1 R values correct 1 All R given to either 2 or either 3 significant figures 1 2(c) 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 2(d) method shown clearly on graph 1 triangle using at least ½ of candidate’s line between extreme plots. 1

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3 In this experiment, you will investigate the cooling of hot water. Complete the following instructions, referring to Fig. 3.1. thermometer beaker bench Fig. 3.1 (a) Use the thermometer to measure the room temperature θR. θR = ......................................................... [1] (b) (i) Pour 200 cm3 of hot water into the beaker. Place the thermometer in the water in the beaker. Record in Table 3.1 the temperature θ of the hot water at time t = 0. Immediately start the stop-watch. Continue recording the temperature and the time in Table 3.1 at 30 s intervals until you have seven sets of readings. [2] (ii) Complete the column headings in Table 3.1. Table 3.1 t / θ / [1] (c) (i) Calculate the decrease in temperature Δθ1 between time t = 0 and time t = 90 s. Δθ1 = ......................................................... [1] (ii) Calculate the difference in temperature ΔθS between the temperature at time t = 0 and room temperature θR. ΔθS = ......................................................... [1] (iii) Calculate the decrease in temperature Δθ2 between time t = 90 s and time t = 180 s. Δθ2 = ............................................................... Calculate the difference in temperature ΔθT between the temperature at time t = 90 s and room temperature θR. ΔθT = ............................................................... [1] (d) A student suggests that the decrease in temperature of the water in 90 s should be greater when the starting temperature is greater. (i) State whether your results agree with this suggestion. Justify your statement by reference to your results. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [2] (ii) Suggest how you would continue the experiment, using the same apparatus and method, to investigate the suggestion. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] [Total: 11]

Mark scheme: 3(a) realistic room temperature (°C) 1 3(b)(i) 0, 30, 60, 90, 120, 150, 180 1 temperatures decreasing 1 3(b)(ii) s, °C 1 3(c)(i) 1 correct 1 3(c)(ii) S correct 1 3(c)(iii) correct values and T < S 1 3(d)(i) statement matches results 1 justification matches statement with numbers correctly quoted 1 3(d)(ii) take additional readings at times beyond 180 s 1 for at least another 180s/until the temperature is close to room temperature or stops decreasing 1

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4 A student investigates the effect of changing the colour of light on the focal length of a lens. uv The focal length f of a lens is given by the equation f = (u + v). The distance u is the distance between an object and the lens. The distance v is the distance between the lens and the image that is formed on a screen. Plan an experiment to investigate the effect of changing the colour of light on the focal length of a lens. You are not required to do this experiment. The following apparatus is available to the student: • illuminated object • a selection of coloured filters to change the colour of the light • converging lens • screen • metre ruler. Other apparatus normally available in a school laboratory can also be used. In your plan, you should: • draw a labelled diagram to show the arrangement of the apparatus • explain briefly how you would do the investigation, including the measurements you would take • draw a suitable table, with column headings, to show how you would display your readings (you are not required to enter any readings in the table) • state how you would use your results to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 MP1 labelled diagram 1 diagram with lens between object and screen, and filter anywhere between the illuminated object and the lens or between the source of illumination and the object, with a least 1 label MP2 method 1 move object / lens / screen to obtain focused / sharp / clear image MP3 measure / record / find / calculate / note u and v 1 MP4 calculate / determine / find the focal length 1 MP5 repeat with different colours / filters 1 MP6 table 1 table with clear columns for (filter) colour, u and v AND with appropriate units MP7 how to reach conclusion 1 plot bar chart of focal length and colour OR compare results to see if / how the change of colour affects the focal length OR compare results to determine the effect of a change in colour on the focal length Additional graph notes: 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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