Cambridge A Level Physics 9702 — 2009 Oct/Nov Paper 3 · Variant 2

This document consists of 9 printed pages and 3 blank pages. DCA (SJF5068/CG) 11663/3 © UCLES 2009 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer both questions. You will be allowed to work with the apparatus for a maximum of one hour for each question. You are expected to record all your observations as soon as these observations are made, and to plan the presentation of the records so that it is not necessary to make a fair copy of them. The working of the answers is to be handed in. Additional answer paper and graph paper should be submitted only if it becomes necessary to do so. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. All questions in this paper carry equal marks. * 6 1 5 6 3 6 7 9 1 9 * PHYSICS 9702/32 Paper 32 Advanced Practical Skills 2 October/November 2009 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

3 9702/32/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use You may not need to use all of the materials provided. 1 In this experiment you will investigate the position of a wooden rod suspended in water as the load on it is varied. Assemble the apparatus as shown in Fig. 1.1 and then fill the beaker to the brim with water. support (if necessary) tray beaker mass attached to rod wooden rod mass hanger 5 springs Fig. 1.1 Adjust the height of the clamp so that the rod is lowered into the water until the mass attached to the bottom of the rod is just covered, as shown in Fig. 1.2. h filled to brim with water mass hanger Fig. 1.2

4 9702/32/O/N/09 © UCLES 2009 For Examiner’s Use (a) Record h, as shown in Fig. 1.2. h = ………………………………… cm (b) Add a mass m to the mass hanger and repeat (a). Repeat this procedure until you have six sets of readings for m and h. Include in your table values for W, where W is the weight of the added mass m. (Use g = 9.81 ms–2.) (c) (i) Plot a graph of W on the y-axis against h on the x-axis, and draw the line of best fit. (ii) Determine the gradient of the line. gradient = …………………………………

5 9702/32/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use

6 9702/32/O/N/09 © UCLES 2009 For Examiner’s Use (d) (i) Use the vernier calipers to determine the diameter d of the wooden part of the rod. d = ………………………………… (ii) Calculate the cross-sectional area A of the wooden part of the rod, using the relationship A = πd 2 4 . A = ………………………………… m2 (e) The relationship between W and h is W = c – h(k + ρAg) where c is a constant, k is the spring constant, ρ is the density of water (1000 kg m–3), and g is the acceleration of free fall (9.81 m s–2). Using your answers from (c)(ii) and (d)(ii), determine the value of k. Give an appropriate unit. k = …………………………………

7 9702/32/O/N/09 [Turn over BLANK PAGE Please turn over for Question 2.

8 9702/32/O/N/09 © UCLES 2009 For Examiner’s Use You may not need to use all of the materials provided. 2 In this experiment you are provided with a ball suspended by a thread so that it is next to a solid vertical surface. You will investigate how the rebound distance is related to the release distance when it swings against the solid surface. (a) Assemble the apparatus as shown in Fig. 2.1, with the thread clamped between the two wooden blocks so that l is about 50 cm, and with the brick positioned so that it is just touching the stationary ball. wooden blocks brick l Fig. 2.1 Measure l. l = …………………………………

9 9702/32/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use (b) (i) Pull back the ball and measure the distance a shown in Fig. 2.2. Do not exceed a = 25 cm. a = ………………………………… cm (ii) Release the ball and make measurements to determine the rebound distance b shown in Fig. 2.2. b = ………………………………… cm wooden blocks brick ball ready to be released ball after rebounding b a Fig. 2.2 (c) (i) Explain how you used the apparatus to ensure that the rebound distance b was measured as accurately as possible. … … … … … (ii) Estimate the percentage uncertainty in b. percentage uncertainty in b = …………………………………

10 9702/32/O/N/09 © UCLES 2009 For Examiner’s Use (d) For values of a less than 25 cm, theory predicts that l – l 2 – b 2 l – l 2 – a 2 k = where k is a constant. Calculate a value for k. k = ………………………………… (e) Repeat (b)(i), (b)(ii) and (d) using a different value of a. a = ………………………………… b = ………………………………… k = ………………………………… (f) Explain whether your results indicate that k is a constant. … … … …

11 9702/32/O/N/09 © UCLES 2009 For Examiner’s Use (g) (i) State four sources of error or limitations of the procedure in this experiment. 1. … … 2. … … 3. … … 4. … … (ii) Suggest four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures. 1. … … 2. … … 3. … … 4. … …

12 9702/32/O/N/09 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2009 question paper for the guidance of teachers 9702 PHYSICS 9702/32 Paper 32 (Advanced Practical Skills 2), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2009 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 32 © UCLES 2009 1 (a) First value for h to nearest mm [1] (b) Measurements table [4] Four marks for six sets of readings for m and h, three for five sets, etc. (–1 if trend is positive, –1 if help from supervisor) Table – range [1] Values of m must be [ 10 g and Y 100 g. Values must include 10 or 20 g and 90 or 100 g with no interval greater than 20 g. Table – column headings [1] Each column heading must contain a quantity and a unit where appropriate. Ignore units in the body of the table. There must be some distinguishing mark between the quantity and the unit (i.e. solidus is expected, but accept, for example, m (g)). Table – consistency of presentation of raw readings [1] All values of h must be given to the same number of decimal places. (c) (i) (Graph) Axes – [1] Sensible scales must be used. Awkward scales (e.g. 3:10) are not allowed. Scales must be chosen so that the plotted points occupy at least half the graph grid in both x and y directions. Scales must be labelled with the quantity which is being plotted. Ignore units. Allow reversed axes but do not allow wrong graph. Gaps between labels must not be greater than three large squares. (Graph) Plotting – [1] All observations must be plotted. Ring and check a suspect plot. Tick if correct. Re-plot if incorrect (i.e. if plot is more than half a small square from the correct position). Do not allow plots with diameter greater than half a small square. (Graph) Line of best fit – [1] Judge by scatter of at least 5 trend plots about the candidate's line. There must be a fair scatter of points either side of the line. Indicate best line if candidate's line is not the best line. (Graph) Quality of results – [1] Judge by scatter of points about a best fit line All points in the table (which must be at least 5) must be within 0.5 ‘h-scale cm’ of a straight line. Do not award if wrong trend. (ii) Gradient – The hypotenuse must be at least half the length of the drawn line. [1] Read-offs must be no more than half a small square from the line (if incorrect, write in correct value). [1] Check for ∆y/∆x. Check value is consistent with trend.

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 32 © UCLES 2009 (d) (i) Measurement – value for raw d in range 18.00 to 27.00 mm (or SV ±2.00 mm), and given to nearest 0.1 mm or nearest 0.01 mm. Unit must be given. [1] Measurement – repeated readings for d. [1] (ii) A calculated correctly. Allow ecf. Check value. Penalise power of ten error. If incorrect, write in the correct value. [1] S.f. in A the same as or one more than the s.f. in raw d. [1] (e) Gradient value from (c)(ii) equated to – (k+ρAg). Allow ecf. Penalise sign error. [1] Value for k in range 3.50 to 6.49 Nm–1 (or SV ±30%). [1] Ignore sign. Unit required. Do not award this mark if the gradient has not been used. [Total: 20]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 32 © UCLES 2009 2 (a) Value of l, with unit, to nearest mm. [1] If SV help, then –1. (b) (i) First value of a (Y 25 cm) [1] (ii) First value of b (less than a) [1] (c) (i) Use named item as marker for rebound distance/ [1] Place ruler under path and view vertically from above/ Use second brick as releasing point. (ii) Percentage uncertainty in b [1] If repeated readings have been done then the uncertainty could be half the range, otherwise absolute uncertainty must be at least 2 mm and no more than 10 mm. Correct ratio idea required. (d) First value of k substitution correct and value <1. There must be no unit. [1] S.f. in value of k – must be 2 or 3 s.f. (but allow 4 s.f. if all raw data is to 3 s.f.) [1] (e) Second values of a and b. [1] Evidence of repeat readings for first or second value of b [1] Second value of b shows correct trend. [1] (f) Calculation of % difference (or equivalent) in k values. [1] Valid conclusion based on the two values of k (e.g. k is constant because values close), consistent with 20% difference as border between ‘close’ and ‘not close’ unless candidate has defined his own % difference. [1]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 32 © UCLES 2009 (g) Identifying limitations and improvements (g) (i) Difficulties (one from each box – max. 4) (g) (ii) Improvements (one from each box – max. 4) But not A Two sets of readings not enough. Take more readings and plot a graph / calculate more k values. Repeated readings. B Difficult to judge rebound point/distance because of movement / short static time. Use video with slow playback / use position sensor to measure rebound / use sound of ball striking a block to judge rebound / use lightgate and refine its position. Use computer or data logger / attach pointer to ball / change length of string / time rebound instead of measuring. C Difficult to release without exerting a force/movement. Named, realistic method of release without a force (e.g. remote-controlled clamp). D Parallax error in measuring rebound distance. Observe shadow on screen. View at eye level. E Inconsistent bounce / ball bounces at an angle. Use smoother brick. Use heavier ball. F Motion affected by air movement / ball swings around. Turn off fans or air con / shield from draughts. Air resistance / carry out in vacuum / constraining guides. G When measuring l it is difficult to judge centre of ball. Suitable method for measuring diameter of ball. [8] [Total: 20]