Cambridge IGCSE Physics 0625 — 2021 Feb/March Paper 5 · Variant 2

1 In this experiment, you will investigate the motion of an oscillating metre rule. Carry out the following instructions, referring to Fig. 1.1. clamps vertical threads l d metre rule stands horizontal bench Fig. 1.1 (a) Ensure that the metre rule is horizontal. You may need to adjust the height of one of the clamps slightly. Briefly describe how you check that the metre rule is horizontal. You may draw a diagram or add to Fig. 1.1 if it helps to explain your answer. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] Do not change the length l of the threads during the experiment. (b) Move one thread to the 40.0 cm mark on the metre rule and one thread to the 60.0 cm mark on the metre rule. The distance d between the threads is 20.0 cm. Move the stands so that the threads remain vertical. Hold each end of the metre rule. Twist the metre rule a small amount, as shown in Fig. 1.2, and then let it go so that it oscillates in a rotating motion. metre rule seen from above one oscillation twist Fig. 1.2 Measure, and record in Table 1.1, the time t for 5 complete oscillations of the metre rule. Repeat this procedure for d values of 30.0 cm, 40.0 cm, 50.0 cm and 60.0 cm. For each value, the threads must be at equal distances either side of the 50.0 cm mark on the metre rule. Table 1.1 1 1 d / cm t / s T s / 20.0 30.0 40.0 50.0 60.0 [2] 1(c) For each value of the distance d, calculate and record in Table 1.1, the value of where T is T the time for 1 oscillation of the metre rule. 1 5 Use your values of time t from Table 1.1 and the equation = . T t [1] 1 1(d) Plot a graph of distance d / cm (y-axis) against (x-axis). T s / [4] (e) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ..................................................... [1] (f) (i) Explain why it is more accurate to measure the time for 5 oscillations rather than for 1 oscillation. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (ii) Describe how the experiment could be improved to make the readings more reliable. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] [Total: 11]

Mark scheme: 1(a) method outlined e.g. measure distance of rule from bench at two places and horizontal if equal 1 1(b) 5 t values in sensible range 1 all decreasing 1 1(c) correct calculations of 1 / T 1 1(d) graph: • axes labelled with quantity and unit 1 • appropriate scales (plots occupying at least ½ grid) 1 • plots all correct to ½ small square and precise plots 1 • well-judged line and thin line 1 1(e) G present and triangle method seen on graph 1 1(f)(i) (timing) errors have less effect / smaller % uncertainty 1 1(f)(ii) repeat each reading and calculate average value 1

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2 In this experiment, you will investigate the cooling of hot water in two different cups. Carry out the following instructions, referring to Fig. 2.1. thermometer lids bench cup A cup B Fig. 2.1 (a) (i) Remove the lid from cup A. Pour 75 cm3 of hot water into cup A and replace the lid. Place the thermometer in the water in cup A. In the first row of Table 2.1, record the temperature θ of the water at time t = 0 and immediately start the stop-clock. Record, in Table 2.1, the temperature θ of the water at times t = 30 s, 60 s, 90 s, 120 s, 150 s and 180 s. [1] (ii) Repeat the steps in (a)(i) for cup B. [2] (b) Table 2.1 cup A cup B t / θ/ θ/ 0 30 60 90 120 150 180 Complete the headings in Table 2.1. [1] (c) Write a conclusion stating which cup, A or B, is the more effective in reducing the cooling rate of the hot water in this experiment. Justify your answer by reference to your results. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) (i) Calculate xA, the average cooling rate for cup A over the whole experiment. Use your readings for cup A from Table 2.1 and the equation θ0 – θ180 xA = T where T = 180 s and θ0 and θ180 are the temperatures at time t = 0 and at time t = 180 s. Include the unit for the cooling rate. xA = ..................................................... [2] (ii) Suggest an additional experiment to show how the lid affects the cooling rate of cup A. Explain how to use the additional results to show the effect. You are not required to carry out this experiment. additional experiment ........................................................................................................ ........................................................................................................................................... explanation ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [2] (e) A student wishes to compare the effect of the materials of the cups on cooling rates. Suggest one variable that she should control to make this test fair. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: 2(a)(i) θ for cup A decreasing 1 2(a)(ii) θ for cup B decreasing and recorded to at least 1 °C 1 decreasing more slowly than θ for cup A 1 2(b) s, °C, °C 1 Question Answer Marks 2(c) statement matching readings in table 1 comparison of temperature changes over 180 s, matching statement 1 2(d)(i) correct calculation of xA 1 unit °C / s 1 2(d)(ii) repeat (cup A) experiment without a lid 1 calculate cooling rate and subtract xA 1 2(e) suitable control: same volume of water, same initial temperature, same dimension of cup, same thickness of material same room temp/named appropriate environmental condition 1

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3 In this experiment, you will investigate a resistor and a lamp connected in series. The circuit has been set up for you with the voltmeter connected to measure the potential difference across the lamp. Carry out the following instructions, referring to Fig. 3.1. power supply resistance wire A crocodile clip V Fig. 3.1 (a) (i) Switch on. Move the crocodile clip on the resistance wire so that the value of the potential difference VL across the lamp is 2.0 V. Measure, and record in Table 3.1, the value of the current I for the lamp and resistor in series. Disconnect the voltmeter and re-connect it so that it measures the potential difference across the resistor. Measure, and record in Table 3.1, the value of the potential difference VR across the resistor. Switch off. Disconnect the voltmeter and re-connect it in its original position across the lamp. [1] (ii) Repeat the steps in (a)(i) for VL = 1.0 V and VL = 0.5 V. [2] Table 3.1 VL / V I / A VR / V RL / Ω RR / Ω 2.0 1.0 0.5 (b) Calculate, and record in Table 3.1, the resistance of the lamp RL for each value of VL. VL Use your values of VL and I from Table 3.1 and the equation RL = I . Calculate, and record in Table 3.1, the resistance of the resistor RR for each value of VL. VR Use your values of VR and I from Table 3.1 and the equation RR = I . [3] (c) A student suggests that RR should be constant. State whether your results support this suggestion. Justify your statement by reference to values from Table 3.1. statement .................................................................................................................................. ................................................................................................................................................... justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] (d) A student wishes to determine the resistance of the lamp RL when the potential difference across the lamp VL = 0.0 V. Describe how the experiment can be extended to do this with the help of a suitable graph. You are not required to carry out this additional experiment. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (e) It is possible to use a variable resistor instead of a resistance wire to change the potential difference across the lamp. Complete the circuit in Fig. 3.2 to show a variable resistor used for this purpose. You are not required to carry out this experiment. power supply A V Fig. 3.2 [1] [Total: 11]

Mark scheme: 3(a)(i) 1 3(a)(ii) VR all decreasing and < 1.0 V 1 I all to 2dp at least and VR all to 1dp at least 1 3(b) correct calculations of RL and RR 1 RL decreasing and RR within 10% of each other 1 RL and RR all consistent 2 or consistent 3 significant figures 1 Question Answer Marks 3(c) statement matching results 1 within limits of experimental accuracy / owtte and supported by relevant values from table 1 3(d) obtain more values and plot a graph of RL vs VL 1 extend line to RL axis and read intercept 1 3(e) correct variable resistor symbol (rectangle with strike-through arrow only) in completed series circuit 1

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4 A student investigates the motion of a ball rolling down a slope. Plan an experiment which enables him to investigate how one factor affects the average speed of the ball. Average speed can be calculated using the equation: distance travelled average speed = time taken You are not required to carry out the experiment. The apparatus available includes: balls of various sizes and materials a board which can act as a slope blocks to support one end of the board. In your plan, you should: • state a factor which can be measured • list any additional apparatus needed • explain briefly how to carry out the experiment including exactly which measurements are to be taken • state the key variables to be kept constant • draw a table, or tables, with column headings, to show how to display the readings (you are not required to enter any readings in the table) • explain how to use the readings to reach a conclusion. You may draw a diagram if it helps to explain your plan. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. .................................................................................................................................................................. ............................................................................................................................................................ [7] [Total: 7]

Mark scheme: 4 MP1 factor: named factor 1 MP2 method: measure time for motion of ball and means of doing so (stopwatch / timer) over measured distance and means of measuring (probably metre rule / tape measure) / mention of between fixed points 1 MP3 repeat for new value of the independent variable 1 MP4 control: any variable appropriate to independent variable e.g. mass of ball if diameter is factor 1 MP5 table: columns, with units, at least for independent variable, time 1 MP6 analysis: compare readings in the table to see if change in factor produces change in speed, plot line graph (with axes specified) 1 MP7 additional point (one from): at least 5 sets of data taken, repeat each measurement and take average, repeat (whole) experiment for same factor but a new condition use of fiducial aid (e.g. mark fixed points to time between) release ball without pushing suitable means of release 1

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