Cambridge IGCSE Physics 0625 — 2019 May/June Paper 6 · Variant 3

1 Some students are determining the mass of a block U by a balancing method. They are using the apparatus shown in Fig. 1.1. b block M block U a 50.0 cm mark pivot metre rule Fig. 1.1 (a) One student places the metre rule on the pivot at the 50.0 cm mark and then places block U with its centre at the 5.0 cm mark. Suggest why it might be difficult to place block U accurately at the 5.0 cm mark. Explain how the student could overcome this difficulty. You may draw a diagram. ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (b) (i) The student places block M on the metre rule as shown in Fig. 1.1 and adjusts the position of block M until the metre rule is as near to being balanced as possible. Briefly describe a method to find the position at which the metre rule is as near to being balanced as possible. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (ii) The student determines the distance a between the centre of block U and the pivot. He also determines the distance b between the centre of block U and the centre of block M. He repeats the procedure for positions of block U at the 10.0 cm, 15.0 cm, 20.0 cm and 25.0 cm marks. His results are shown in Table 1.1. Table 1.1 position of a / cm b / cm block U / cm 5.0 45.0 65.5 10.0 40.0 59.0 15.0 35.0 51.8 20.0 30.0 45.0 25.0 25.0 38.6 Plot a graph of b / cm (y-axis) against a / cm (x-axis). You do not need to start the axes at the origin (0,0). [4] (c) (i) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = ........................................................ [1] (ii) Calculate the mass MU of block U using the equation MU = (G – 1) × k, where k = 200 g. Record the value of MU to a suitable number of significant figures for this experiment. MU = ........................................................ [2] (d) A student suggests that a and b are proportional. State whether the results support this suggestion. Justify your statement by reference to some results from Table 1.1. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] [Total: 11]

Mark scheme: 1(a) (difficult to see centre of block) and valid method, e.g. • (measure width of block and) add ½ width to 5.0 cm to find position for edge of block • mean value of marks at both edges of mass • mark centre line of mass and align with mark on rule 1 1(b)(i) move block back and forth to find the point of balance / owtte 1 1(b)(ii) graph: axes labelled correct orientation, with quantity and unit 1 appropriate scales (plots occupying at least ½ grid) 1 plots all correct to less than ½ small square and precise plots 1 well-judged line and thin line 1 1(c)(i) G present and triangle method seen on graph 1 1(c)(ii) MU in range 61.0 to 81.0 (g) 1 2/3 sig figs and unit 1 1(d) a and b are proportional 1 b/a constant within limits of experimental accuracy / owtte 1

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2 A student is investigating the transfer of thermal energy between hot water in a beaker and cold water in a glass boiling tube. He is using the apparatus shown in Fig. 2.1. thermometers glass boiling tube clamp stand beaker bench 4 30 20 10 0 Fig. 2.1 (a) Record the room temperature θR, shown on the thermometer in the boiling tube. θR = ........................................................ [1] (b) The student pours cold water into the boiling tube and hot water into the beaker. He places the boiling tube into the beaker of hot water. He then records the temperatures θC of the water in the boiling tube and the temperatures θH of the water in the beaker every 30 s. His readings are shown in Table 2.1. (i) Complete the headings and the time column in Table 2.1. [2] (ii) It is difficult to read both thermometers every 30 s. Describe briefly a technique that would ensure the temperature readings are as accurate as possible in the experiment. ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] Table 2.1 difference in boiling tube beaker temperature - t / θC / θH / (θH θC) / 0 19.5 88.5 69.0 31.0 83.0 52.0 39.5 80.0 40.5 47.5 77.5 30.0 54.0 75.5 21.5 59.0 74.0 15.0 63.0 73.0 10.0 (c) Write a conclusion stating how the difference in temperature between the cold water and the hot water affects the rate of heating of the water in the boiling tube. Justify your answer by reference to the readings. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (d) (i) State what you expect the temperature in the boiling tube will be when θC stops rising. Justify your answer by reference to the readings. statement .......................................................................................................................... justification ........................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... [2] (ii) State what you predict the temperature θH of the water in the beaker will be after a few hours. θH = ........................................................ [1] (e) Suggest two changes that could be made to the apparatus or the procedure to ensure that the temperature θC of the cold water in the boiling tube rises more quickly. 1. ............................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... 2. ............................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... [2] [Total: 11]

Mark scheme: 2(a) 21 (°C) 1 2(b)(i) s, °C, °C, °C all correct 1 30, 60, 90, 120, 150, 180 1 2(b)(ii) any one from: • place stop-clock and thermometers so seen easily • keep eyes at level to thermometer scales • use an audible 30 s alarm • read temperatures alternately every 15 s • use of data logger 1 2(c) greater temperature difference causes greater (rate of) heating 1 comparison of temperature changes during same period in first half and in second half of experiment 1 2(d)(i) within range 64 to 72 (°C) inclusive 1 justification with reference to hot and cold water trends 1 2(d)(ii) 21 (°C) / room temperature 1 2(e) any two from: • thinner walls on tube • metal tube • bung/lid on tube • insulate sides of beaker/lid on beaker • higher initial hot water temperature • lower initial cold water temperature • increase volume of hot water • decrease volume of cold water • stirring 2

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3 Some students are investigating a circuit containing different resistors. They are using the circuit shown in Fig. 3.1. power supply A X Y Z Fig. 3.1 (a) On Fig. 3.1, draw the symbol for a voltmeter connected to measure the potential difference V across resistor X. [1] (b) A student connects the voltmeter as described in (a) and measures the current I in the circuit and the potential difference V across resistor X. 0.4 0.6 2 3 0.2 0.8 1 4 0 1.0 0 5 A V Fig. 3.2 Fig. 3.3 Read, and record in Table 3.1, the values of I and V shown on the meters in Fig. 3.2 and in Fig. 3.3. Table 3.1 resistor I / V / R / combination X X and Y 0.23 3.3 X, Y and Z 0.21 5.0 The student connects the voltmeter to measure the potential difference V across the combination of resistors X and Y together and then X, Y and Z together. Her readings are shown in Table 3.1. Complete the headings in Table 3.1. [3] (c) A student suggests that the current should remain constant when the voltmeter is used to measure potential differences across the different combinations of resistors. State whether the readings in Table 3.1 support this suggestion. Justify your answer by reference to the readings. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [1] (d) (i) Calculate, and record in Table 3.1, the resistance R of each combination of resistors. Use the readings from Table 3.1 and the equation R = V . I [2] (ii) For resistors in series, the total resistance of the combination is the sum of the individual resistances. Use your results from Table 3.1 to calculate the resistances RY and RZ of resistors Y and Z. RY = .............................................................. RZ = .............................................................. [1] (e) (i) The circuit components are to be rearranged so that • resistors X, Y and Z are in parallel • the ammeter will measure the current in the circuit • the voltmeter will measure the potential difference across the resistors. In the space below, draw a diagram of this circuit. [2] (ii) One student sets up the circuit as described in (e)(i). She measures the current IP in the circuit and the potential difference VP across the resistors. She uses these values to calculate the resistance RP of the resistors in parallel. 2.31 Ω RP = .......................................................... Use the student’s result and your result from Table 3.1 to compare RP with the resistance RS of the three resistors connected in series. Tick the box next to the description that most closely matches the results. RP = RS RP = 10RS 10RP = RS None of these descriptions apply [1] [Total: 11]

Mark scheme: 3(a) correct voltmeter symbol in parallel with X 1 3(b) I = 0.22 (A) 1 V = 1.1 (V) 1 A, V, Ω 1 3(c) statement matching results and ‘currents the same within limits of experimental accuracy’ / owtte 1 3(d)(i) R values 5.0/ecf, 14(.3478), 24/(23.8095) (Ω) 1 consistent 2 or consistent 3 sig figs 1 3(d)(ii) RY = 9.0 (Ω) and RZ = 10 (Ω) 1 3(e)(i) 3 resistors in parallel arrangement and circuit symbols correct 1 voltmeter and ammeter in correct arrangement and circuit symbols correct 1 3(e)(ii) 10RP = RS 1

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4 A student wants to investigate the factors that affect the height to which a ball bounces when it is dropped. Plan an experiment that will enable him to investigate in detail how the height from which a ball is dropped affects how high it bounces. The apparatus available includes: balls of different materials and sizes sheets of different floor coverings. Write a plan for the experiment. In your plan, you should: • list any additional apparatus needed • explain briefly how you would carry out the experiment • describe a precaution which could be taken to ensure that measurements of the height of bounce are reliable • state the key variables that you would control • draw a table, 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 could analyse your readings to reach a conclusion. You may draw a diagram if it helps to explain your plan. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7] [Total: 7]

Mark scheme: 4 MP1 Apparatus metre rule / measuring tape 1 MP2 Method drop ball from measured height measure height of bounce repeat for different height of release 1 MP3 Precaution any one from: • repeat (for each height of release) and average • measure to same part of ball each time • measure height of bounce at eye level • release without throwing/impeding • use of video (for height of bounce) 1 MP4 Control variable any one from: • same (diameter/mass/material) ball • type of floor covering 1 MP5 Table columns for release height and bounce height and units 1 MP6 Analysis any one from: • suitable analysis of readings • draw a suitable graph of drop height against bounce height 1 MP7 Additional point any one from: • additional control variable • at least 5 sets of data taken • repeat experiment for different diameter of ball/floor covering • automatic release to eliminate differences 1

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