Cambridge IGCSE Physics 0625 — 2015 May/June Paper 5 · Variant 2

1 In this experiment, you will investigate a pendulum. Carry out the following instructions referring to Figs. 1.1 and 1.2. 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 = 50.0 cm. The length l is measured to the centre of the bob. State one precaution that you took to measure the length l as accurately as possible. You may draw a diagram. ................................................................................................................................................... ...............................................................................................................................................[1] (b) (i) Displace the pendulum bob slightly and release it so that it swings. Measure the time t for 20 complete oscillations of the pendulum (see Fig. 1.2). t = .......................................................... [1] (ii) Calculate the period T of the pendulum. The period is the time for one complete oscillation. T = ...........................................................[1] (iii) Explain why measuring the time for 20 oscillations, rather than for 1 oscillation, gives a more accurate value for T. ........................................................................................................................................... .......................................................................................................................................[1] (c) Adjust the length of the pendulum until its length l = 100.0 cm. Repeat steps (b)(i) and (b)(ii). t = ............................................................... T = ............................................................... [2] (d) A student suggests that doubling the length l of the pendulum should double the period T. State whether your results support this suggestion. Justify your answer by reference to the results. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [2] (e) To continue the investigation of the relationship between the length l of the pendulum and the period T, it is necessary to use a range of values of length l. List additional l values that you would plan to use in the laboratory. You are not asked to make any more measurements. ...............................................................................................................................................[2] [Total: 10]

Mark scheme: 1 (a) any one from: • reference to how to determine the centre of the bob • measure to top of bob then add on half diameter measured with blocks and rule or callipers • measure to top and bottom of bob and average • reference to perpendicular viewing (reducing parallax) • rule parallel with/close to string/appropriate use of set-square [1] (b) (i) t value in range 27.6 to 29.2 (s) (showing correct l and 20T measured) [1] (ii) correct T value = t÷20 calculated, allow ecf from (i) [1] (iii) reduce effect of errors in starting/stopping stopwatch [1] (c) t and T values recorded, correct units seen and not contradicted [1] T value 2.0 ± 0.1 s OR approximately 1.4 × value in (b)(ii) [1] (d) statement to match results (expect no) [1] justification using results, including idea of difference is beyond limits of experimental uncertainty owtte [1] (e) minimum of three more values [1] all values ≥ 20 cm and ≤ 300 cm, and three values are at least 10 cm apart [1] [Total: 10]

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2 In this experiment, you will investigate the cooling of water. Carry out the following instructions referring to Fig. 2.1. thermometer water beaker A Fig. 2.1 (a) Pour 100 cm3 of hot water into beaker A. Place the thermometer in beaker A, as shown in Fig. 2.1. (i) Record the temperature θH of the hot water in beaker A. θH = ...........................................................[1] (ii) State one precaution that you took to ensure that the temperature reading for the hot water is as reliable as possible. ........................................................................................................................................... .......................................................................................................................................[1] (b) (i) Add 50 cm3 of cold water to the hot water in beaker A. Stir briefly. Record the temperature θ1. θ1 = ............................................................... (ii) Calculate the decrease in temperature θA using the equation θA = (θH – θ1). θA = ............................................................... [2] (c) (i) Add a further 100 cm3 of cold water to the water in beaker A. Stir briefly. Record the temperature θ2. θ2 = ............................................................... (ii) Calculate the decrease in temperature θB using the equation θB = (θ1 – θ2). θB = ............................................................... [2] (d) Suggest two factors, other than the volume and temperature of the cold water added, that affect the decrease in temperature of the hot water. 1. ............................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... [2] (e) Describe briefly how a measuring cylinder is read to obtain an accurate value for the volume of water. You may draw a diagram. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ...............................................................................................................................................[2] [Total: 10]

Mark scheme: 2 (a) (i) sensible hot water temperature [1] (ii) any one from: • wait for thermometer reading to stop rising • perpendicular viewing of scale • stirring • thermometer bulb in middle of water/not touching beaker [1] (b) (i) θ1 < θH [1] (ii) θA correct [1] (c) (i) θ2 < θ1 [1] (ii) θB correct and temperatures in °C seen and not contradicted [1] (d) any two from: • room temperature/other environmental statement; • initial hot water temperature; • heat loss to surroundings /evaporation/conduction through sides of beaker; • time delays in adding water [max.2] (e) perpendicular viewing/eye level with meniscus [1] reading to bottom of meniscus [1] [Total: 10]

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3 In this experiment, you will investigate the resistance of lamps. The circuit shown in Fig. 3.1 has been set up for you. power supply A V Fig. 3.1 (a) (i) Switch on. Measure and record the potential difference VP across the lamps and the current IP in the circuit. Switch off. VP = ............................................................... IP = ............................................................... [2] VP (ii) Calculate the combined resistance RP of the lamps using the equation RP = . IP RP = ...........................................................[1] (b) Disconnect and remove one of the lamps. The remaining components are to be arranged to make a circuit in which • the two lamps are in series • the ammeter will measure the total current in the circuit • the voltmeter will measure the potential difference across both lamps. In the space below, draw a diagram of this circuit using standard circuit symbols. [2] (c) Set up the circuit as described in (b). (i) Switch on. Measure and record the potential difference VS across the two lamps and the current IS in the circuit. Switch off. VS = ............................................................... IS = ............................................................... [1] VS (ii) Calculate the resistance RS of the lamps using the equation RS = . IS RS = ...........................................................[2] (d) (i) A student wishes to vary the current in the circuit in Fig. 3.1, using a variable resistor. In the space below, draw the standard circuit symbol for a variable resistor. [1] (ii) On Fig. 3.1, label with X a suitable position in the circuit for a variable resistor used to vary the current in all the lamps. [1] [Total: 10]

Mark scheme: 3 (a) (i) VP to at least 1 d.p. and < 4 V [1] IP to at least 2 d.p. and < 1 A [1] (ii) RP calculated correctly [1] (b) lamps in series [1] voltmeter in correct position, with rest of circuit and symbols correct [1] (c) (i) VS and IS recorded with correct units, AND Ω for RS [1] (ii) RS correct to 2 or 3 significant figures [1] RP < RS by a factor of more than 3 [1] (d) (i) correct symbol for variable resistor NOT potentiometer [1] (ii) X correctly positioned [1] [Total: 10]

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4 In this experiment, you will investigate reflection using a plane mirror. Carry out the following instructions, referring to Fig. 4.1. hole N A e M R 30° B L ray-trace sheet eye Fig. 4.1 (a) Draw a line 10 cm long near the middle of the blank ray-trace sheet supplied. Label the line MR. Draw a normal to this line that passes through its centre. Label the normal NL. Label the point at which NL crosses MR with the letter A. (b) Draw a line 8 cm long from A at an angle of incidence i = 30° to the normal, below MR and to the left of the normal. Label the end of this line B. (c) Place the reflecting face of the mirror vertically on the line MR. (d) Place two pins P1 and P2 on line AB a suitable distance apart. (e) View the images of pins P1 and P2 from the direction indicated by the eye in Fig. 4.1. Place two pins P3 and P4, some distance apart, so that pins P3 and P4, and the images of P1 and P2, all appear exactly one behind the other. Label the positions of P3 and P4. (f) Remove pins P3 and P4 and the mirror. Draw the line joining the positions of P3 and P4. Extend the line until it meets NL. (g) Measure, and record in Table 4.1, the angle α between NL and the line joining the positions of P3 and P4. At this stage the angle θ between the mirror and line MR is 0 °, as shown in the table. (h) Remove pins P1 and P2. Draw lines at angles θ = 10 °, 20 ° and 30 ° to MR, one of which is shown in Fig. 4.1. Repeat steps (d) to (g), placing the mirror on each of the new lines in turn, so that you obtain four sets of readings. Table 4.1 θ/ ° α/ ° 0 10 20 30 [1] (i) Plot a graph of α/ ° (y-axis) against θ/ ° (x-axis). [4] (j) State whether your graph line shows that the angle α is directly proportional to the angle θ. Justify your statement by reference to your graph line. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... [2] Tie your ray-trace sheet into this Booklet between pages 10 and 11. [3] [Total: 10]

Mark scheme: 4 (a)–(h) Ray-trace: • normal at 90° in correct position and angle of incidence 30° ± 1° [1] • all lines present and neat [1] • P1P2 distance > 5.0 cm [1] Table: α values correct: 30°, 50°, 70°, 90° all ± 4° [1] (i) Graph: • axes correctly labelled, right way round and with units [1] • suitable scales, plots occupying at least ½ of grid in both directions [1] • all plots correct to within ½ small square [1] • good best-fit line judgement, thin, continuous [1] (j) NO [1] matching justification referring to line through origin [1] [Total: 10]

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