Cambridge IGCSE Physics 0625 — 2013 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will investigate pendulums. For Examiner’s Carry out the following instructions, referring to Figs. 1.1 and 1.2. Use clamp clamp l bob one complete oscillation Fig. 1.1 Fig. 1.2 A pendulum has been set up for you. (a) Adjust the pendulum until its length l = 30.0 cm. The length l is measured to the centre of the bob. (b) Displace the pendulum bob slightly from its vertical position and release it so that it swings. Measure and record in Table 1.1 the time t for 20 complete oscillations of the pendulum (see Fig. 1.2). (c) Calculate the period T of the pendulum. The period is the time for one complete oscillation. Record the value of T in the table. (d) Adjust the length of the pendulum until its length l = 60.0 cm. Repeat steps (b) and (c). Table 1.1 l / cm t / s T / s 30.0 60.0 [4] (e) A student suggests that doubling the length l of the pendulum should double the For period T. Examiner’s Use State whether your results support this suggestion and justify your answer by reference to the results. statement ......................................................................................................................... justification ....................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... [2] (f) Another student suggests that l should be directly proportional to T 2. The student plots a graph of l against T 2. State two pieces of information from the graph that would indicate that l is directly proportional to T 2. 1. ...................................................................................................................................... 2. ...................................................................................................................................... [2] (g) Remove the pendulum and replace it with the other pendulum provided. This pendulum has a mass that is double the mass of the first pendulum. Adjust the length of the pendulum until its length l = 30.0 cm. Repeat steps (b) and (c). Record the readings in Table 1.2. Table 1.2 l / cm t / s T / s 30.0 [1] (h) Suggest a conclusion about the effect of doubling the mass of the pendulum. .......................................................................................................................................... ..................................................................................................................................... [1] [Total: 10]

Mark scheme: 1 (a) – (d) table: two t values [1] two correct T values [1] both T values to 2 significant figures, or both to 3 significant figures, or both to 4 significant figures [1] first t value 20 s – 24 s [1] (e) statement matches results (expect NO) [1] justification using idea of within or beyond limits of experimental accuracy [1] (f) straight line [1] through the origin [1] (g) t value similar to first row of Table 1.1 ∆t 1 s or less [1] (h) has no effect do not accept approximately the same [1] [Total: 10]

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2 In this laboratory investigation, you will investigate the cooling of water by four different For methods. Examiner’s Use You are provided with a supply of hot water. Experiment A (cooling with stirring). (a) (i) Pour approximately 200 cm3 of the hot water supplied into beaker 1. Place the thermometer in the beaker of water. When the thermometer reading stops rising, record the temperature θ1. θ1 = ....................................................... (ii) Start the stopclock and stir the water for one minute. Record the temperature θ2 of the water. θ2 = ....................................................... (iii) Calculate the temperature difference (θ1–θ2). (θ1–θ2) = ...................................................... [3] Experiment B (cooling with pouring). (b) (i) Empty beaker 1. Pour approximately 200 cm3 of the hot water supplied into beaker 2. Place the thermometer in the beaker of water. When the thermometer reading stops rising, record the temperature θ3. θ3 = ....................................................... (ii) Remove the thermometer. Carefully pour the water from beaker 2 into beaker 1. Pour the water back into beaker 2. Repeat this process four times. (iii) Place the thermometer in the beaker of water. Record the temperature θ4 of the water. θ4 = ....................................................... (iv) Calculate the temperature difference (θ3– θ4). (θ3– θ4) = ....................................................... [1] Experiment C (cooling with a lid) and Experiment D (cooling without a lid). (c) (i) Empty both beakers. (ii) Pour approximately 200 cm3 of the hot water supplied into beaker 1. Place the thermometer in the beaker of water. When the thermometer reading stops rising, record the temperature θ5. θ5 = ....................................................... (iii) Pour approximately 200 cm3 of the hot water supplied into beaker 2. Place the For thermometer in the beaker of water. When the thermometer reading stops rising, Examiner’s measure the temperature θ6. Use θ6 = ....................................................... (iv) Place the lid on beaker 1. Start the stopclock. Allow both beakers to cool for 3 minutes. (v) At the end of the 3 minute cooling period, record the temperature θ7 of the water in beaker 1 and the temperature θ8 of the water in beaker 2. θ7 = ....................................................... θ8 = ....................................................... (vi) Calculate the temperature difference (θ5– θ7). (θ5– θ7) = ...................................................... (vii) Calculate the temperature difference (θ6– θ8). (θ6– θ8) = ....................................................... [3] (d) Rank the experiments in order with the one that produced the greatest temperature drop first. greatest temperature drop 1. ...................................................... 2. ...................................................... 3. ...................................................... smallest temperature drop 4. ...................................................... [1] (e) If this laboratory investigation is to be repeated many times to check the results, suggest one condition that should be kept constant in order to provide reliable results. ..................................................................................................................................... [1] (f) A student complains that the investigation is not a fair comparison. Suggest one way in which the investigation could be made more fair. .......................................................................................................................................... ..................................................................................................................................... [1] [Total: 10]

Mark scheme: 2 (a) (i) sensible value of θ1 [1] (ii) θ2 value lower than θ1 [1] (iii) (θ1 – θ2) correct; unit oC at least once; not contradicted [1] (b) new values all present; greater temperature difference than (a) [1] (c) new values all present [1] sensible and similar temperatures for θ5 and θ6 [1] temperature difference in (vi) less than in (vii) [1] (d) order matches results [1] (e) any one from: room temperature or other environmental condition initial (hot) water / starting temperature volume / mass / amount / level of (hot) water same type / thickness / material / size / volume of beaker time delays during operations [1] (f) same time of cooling for each experiment [1] [Total: 10] IGCSE – October/November 2013 0625 52

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3 In this experiment, you will investigate the resistance of a wire. For Examiner’s Carry out the following instructions, referring to Fig. 3.1 which shows the circuit that has Use been set up for you. power supply A x A B C resistance wire metre rule V Fig. 3.1 You are provided with a length of resistance wire AB. (a) (i) Place the sliding contact C on the resistance wire AB at a distance x from A, where x = 0.200 m. (ii) Record the value of x in Table 3.1. (iii) Switch on. Measure the potential difference V across the wire between A and C. Record the value of V in Table 3.1. (iv) Measure the current I in the wire. I = .................................................. [1] (v) Take the sliding contact away from the wire AB and switch off. V (vi) Calculate the resistance R of the section AC of the wire using the equation R = . I Record R in Table 3.1. Table 3.1 x / m V / V R / Ω [3] (b) Repeat the steps in (a) with the sliding contact at distances x = 0.350 m, 0.500 m, For 0.650 m and 0.800 m from A. Examiner’s Use (c) Plot a graph of R / Ω (y-axis) against x / m (x-axis). [4] (d) Using your graph, determine the length l of the resistance wire necessary to make a resistor of resistance 1.2 Ω. Show clearly on your graph how you obtained the necessary information. l = .................................................. [1] (e) Predict the resistance Z of 1.50 m of the resistance wire. Show your working. Z = .................................................. [1] [Total: 10]

Mark scheme: 3 (a) I to at least 2 d.p. and < 1 A; unit A [1] (b) table: x values 0.200, 0.350, 0.500, 0.650, 0.800 [1] all V to at least 1 d.p. and < 3 V [1] R values correct [1] (c) graph: axes correctly labelled, right way around [1] suitable scales [1] all plots correct to ½ small square [1] good line judgement, thin continuous line, neat plots [1] (d) correct value to half a square – must see evidence on graph paper [1] condone no/incorrect unit (e) sensible value from candidate’s results [1] [Total: 10]

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4 In this experiment, you will determine the focal length of a converging lens. For Examiner’s Carry out the following instructions, referring to Fig. 4.1. Use illuminated u v object screen lens Fig. 4.1 (a) (i) Place the lens a distance u = 20.0 cm from the illuminated object. Move the screen until a sharply focused image of the object is seen on the screen. The screen and the illuminated object must now remain in the same positions during the experiment. (ii) Measure and record the distance v from the centre of the lens to the screen. v = .................................................. [1] (iii) Calculate the value of uv. uv = ....................................................... (iv) Calculate the value of (u + v). (u + v) = ...................................................... uv (v) Calculate a value f1 for the focal length of the lens, using the equation f1 = (u + v). f1 = ....................................................... [2] (b) (i) Do not move the position of the screen or the illuminated object. Move the lens towards the screen until a smaller, sharply focused image of the object is seen on the screen. (ii) Measure and record the distance v from the centre of the lens to the screen. v = ....................................................... (iii) Measure and record the distance u from the centre of the lens to the illuminated For object. Examiner’s Use u = ....................................................... (iv) Calculate the value of uv. uv = ....................................................... (v) Calculate the value of (u + v). (u + v) = ....................................................... [1] (vi) Calculate a second value f2 for the focal length of the lens, using the equation uv f2 = (u + v). f2 = .................................................. [1] (c) A student suggests that f1 should be equal to f2. State whether your results support this suggestion and justify your answer by reference to the results. statement ......................................................................................................................... justification ....................................................................................................................... .......................................................................................................................................... [2] (d) State two precautions that you could take in this experiment to obtain reliable results. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... .......................................................................................................................................... [2] Question 4 continues on the next page (e) Sketch a diagram of the image seen in part (b). For Examiner’s Use [1] [Total: 10]

Mark scheme: 4 (a) (i) v = 58 – 62 (cm) [1] (iii) (iv) calculations correct [1] (v) f1 correct 2 or 3 significant figures AND unit [1] (b) (ii) – (v) sensible new set of readings and results, with v within 2 cm of previous u (20.0 ± 2.0 cm) [1] (vi) f1 and f2 within 4 cm of each other [1] (c) statement matches results (expect YES) [1] justification in terms of within or beyond limits of experimental accuracy [1] (d) any two from: use of darkened room / brighter lamp / no other lights mark position of centre of lens on holder place metre rule on bench (or clamp in position) ensure object and (centre of) lens are same height (from the bench) lens / object / screen, vertical or perpendicular (to bench) repeat (and average) move the lens slowly when focusing o.w.t.t.e. [2] (e) image drawn inverted [1] [Total: 10]

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