Cambridge IGCSE Physics 0625 — 2011 Oct/Nov Paper 5 · Variant 2

1 In this experiment, you will investigate the principle of moments. For Examiner’s Carry out the following instructions referring to Fig. 1.1. Use d x y zero 50.0 cm mark metre rule end modelling pivot clay Fig. 1.1 You are provided with a piece of modelling clay. (a) Mould the piece of modelling clay into a cube shape. Place the modelling clay on the rule so that its centre is at a distance d = 10.0 cm from the zero end of the rule as shown in Fig. 1.1. Adjust the position of the rule so that it is as near as possible to being balanced, with the 50.0 cm mark to the right of the pivot. (i) Measure the distance x from the centre of the modelling clay to the pivot. x = ...................................................... (ii) Measure the distance y from the pivot to the 50.0 cm mark on the rule. y = ...................................................... (iii) The mass M of the metre rule is provided for you on a card. Record this value. M = ...................................................... (iv) Calculate the mass m1 of the piece of modelling clay using the equation My m1 = x . m1 = ...................................................... [3] (b) Divide the modelling clay into two pieces, with one piece approximately twice the size of For the other piece. Examiner’s Use (i) Using the larger piece of modelling clay, of mass m2, repeat the steps in (a). x = ...................................................... y = ...................................................... m2 = ...................................................... (ii) Using the smaller piece of modelling clay, of mass m3, repeat the steps in (a). x = ...................................................... y = ...................................................... m3 = ...................................................... (iii) Calculate m2 + m3. m2 + m3 = ...................................................... [4] (c) Assuming that the experiment has been carried out with care, suggest two reasons why m2 + m3 may not be equal to m1. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] (d) Explain briefly how you ensured that the centre of the cube of modelling clay was at the 10.0 cm mark on the metre rule. You may draw a diagram. .......................................................................................................................................... .......................................................................................................................................... ......................................................................................................................................[1] [Total: 10]

Mark scheme: 1 (a) x and y values present both less than 40 cm [1] x and y consistently in either mm, cm or m [1] m1 correct in g, with unit [1] (b) two new sets of x, y and m; both x + y = 40 ± 0.5cm [1] second new set of x, y and m (m3 < m2) [1] m2 + m3 correct (= m1 ± 2g) [1] correct unit for x and y at least once (in (a) or (b)) [1] (c) two from: modelling clay remaining on knife/rule/fingers/lost in cutting NOT just ‘dropped’/‘lost’ – must mention cutting more difficult to balance with smaller pieces any explicit idea of why two pieces not so accurate more readings so more inaccuracies rounding errors in extra calculations difficult to find centre of misshapen cube modelling clay might not have uniform density [2] (d) mark centre of bottom of cube / take readings at either side of cube [1] [Total: 10]

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2 In this experiment, you will investigate temperature changes when hot and cold water are For mixed. Examiner’s Use You are provided with a supply of hot water and a supply of cold (room temperature) water. (a) (i) Pour 100 cm3 of hot water into the beaker labelled A. Measure and record the temperature θh of the water in beaker A. θh = ...................................................... (ii) Measure and record the temperature θc of the cold water supplied. θc = ...................................................... (b) (i) Add 10 cm3 of the cold water to the water in beaker A. Briefly stir the water in beaker A. (ii) Measure and record in Table 2.1 the temperature θm of the water in beaker A. Also record the volume V of water added. (iii) As soon as possible repeat step (b)(i) five times. Each time add 10 cm3 of cold water to the water already in beaker A until a total of 60 cm3 has been added. Each time record in the table the temperature θm of the water in beaker A and the total volume V of water added so far. Table 2.1 V / cm3 θm / °C [3] (c) Plot the graph of θm / °C (y-axis) against V / cm3 (x-axis). Include on your graph the For temperature θh at volume V = 0, as recorded in (a)(i). Examiner’s Use [4] (d) If this experiment were to be repeated in order to check the results, it would be important to control the conditions. Suggest two such conditions that should be controlled. 1. ...................................................................................................................................... 2. ..................................................................................................................................[2] (e) Suggest a practical precaution that will enable readings in this experiment to be taken as accurately as possible. .......................................................................................................................................... ......................................................................................................................................[1] [Total: 10]

Mark scheme: 2 (a) θh and θc sensible values [1] (b) correct V values in table 10, 20, 30, 40, 50, 60 [1] θm values decreasing and all between θr and θh [1] (c) graph: axes labelled and scales suitable [1] all plots correct to nearest ½ small square [1] well-judged best-fit line [1] thin line and small plots [1] (d) any two from: same hot water temperature/initial temperature constant room/surrounding temperature/other suitable named environmental condition constant cold water temperature same amount/rate of stirring time taken for transfer or wtte [2] (e) any one from: avoidance of parallax explained (thermometer or measuring cylinder) wait for temperature to stabilise [1] [Total: 10] IGCSE – October/November 2011 0625 52

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3 In this experiment, you will investigate the potential difference across resistors in a circuit. For Examiner’s Carry out the following instructions referring to Fig. 3.1. The circuit is set up for you. Use power source A R2 R1 R3 Fig. 3.1 (a) (i) Switch on. Use the voltmeter to measure the potential difference VA across resistor R1. VA = ...................................................... (ii) Measure the potential difference VB across resistors R2 and R3. VB = ...................................................... (iii) Measure the potential difference VC across the combination of the three resistors. VC = ...................................................... [4] Switch off. (b) Theory suggests that VC = VA + VB. For Examiner’s (i) Calculate VA + VB. Use VA + VB = ...................................................... (ii) State whether your experimental results support the theory and justify your statement by reference to your results. statement ................................................................................................................. justification ............................................................................................................... .................................................................................................................................. ..............................................................................................................................[3] (c) (i) Switch on. Record the current I indicated on the ammeter. I = ...................................................... Switch off. (ii) Calculate the resistance R of the combination of the three resistors using the equation R = VC . I R = ................................................. [2] (d) On Fig. 3.1 draw in the voltmeter connected as required in (a)(iii) using the standard symbol for a voltmeter. [1] [Total: 10]

Mark scheme: 3 (a) all V values to 1 decimal place or better and < 2.5V [1] unit at least once and not contradicted [1] VA > VB [1] VC > VA and VC > VB [1] (b) VA + VB = VC (within 10%) [1] correct statement matching results [1] justification matching statement and referring to results [1] (c) I sensible value and to at least 2 decimal places [1] R correct (ecf), 2 or 3 significant figures, with unit [1] (d) voltmeter correctly shown [1] [Total: 10]

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4 In this experiment, you will investigate the reflection of light by a plane mirror. For Examiner’s Carry out the following instructions referring to Fig. 4.1. Use M N R A C B L 3.0 cm ray trace sheet eye Fig. 4.1 (a) Draw a line 16 cm long near the top of the ray trace sheet. Label the line MR. Draw a normal to this line that passes through its centre. Label the point at which the normal crosses MR with the letter N. (b) Draw a line 16 cm long parallel to and 10 cm below the line MR. Label this line AB. Label the point at which the normal crosses this line with the letter L. (c) Place the mirror, with its reflecting face vertical, on the line MR. The mirror has a line drawn on it. One end of this line must be at point N. (d) Place a pin P1 on line AB at a point 3.0 cm to the left of the normal. Label this point C. (e) View the line on the mirror and the image of pin P1 from the direction indicated by the For Examiner’s eye in Fig. 4.1. Place two pins P2 and P3 some distance apart so that the image of P1, the line on the mirror, and pins P2 and P3, all appear exactly one behind the other. Label Use the positions of P2 and P3. (f) Remove the pins and the mirror and draw in the line joining the positions of P2 and P3. Continue the line until it meets the normal. Draw in the line joining point C and point N. (g) Measure, and record in Table 4.1, the angle of incidence i between the normal and the line CN. Measure, and record in the table, the angle of reflection r between the normal and the line passing through P2 and P3. (h) Repeat the steps (d) – (g) using a position of P1 5.0 cm from the normal. Table 4.1 i / ° r / ° [3] (i) In spite of carrying out this experiment with reasonable care, it is possible that the values of the angle of reflection r will not be exactly the same as the values obtained from theory. Suggest two possible causes of this inaccuracy. 1. ...................................................................................................................................... .......................................................................................................................................... 2. ...................................................................................................................................... ......................................................................................................................................[2] Tie in your ray trace sheet between pages 10 and 11. [5] [Total: 10]

Mark scheme: 4 trace: (a) normal at 90° to MR in correct position [1] (b)–(h) all lines neatly drawn in correct position [1] AB in correct position [1] both P2P3 distances [ 5.0cm [1] P1 positions correct [1] (g) table: i values correct [1] r values correct [1] all i = r (within 4°) [1] (i) any two from: thickness of lines thickness of pin holes/pins thickness of mirror thickness of protractor [2] [Total: 10]

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