Cambridge A Level Physics 9702 — 2007 May/June Paper 3 · Variant 1

This document consists of 9 printed pages and 3 blank pages. MML 12308 12/05 T19383/3 © UCLES 2007 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Secondary Education Advanced Subsidiary Level and Advanced Level * 8 5 9 6 0 6 9 3 7 3 * PHYSICS 9702/31 Paper 31 Advanced Practical Skills 1 May/June 2007 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all 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 ON 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. For Examiner’s Use 1 2 Total

3 9702/31/M/J/07 [Turn over For Examiner’s Use © UCLES 2007 You may not need to use all of the materials provided. 1 In this experiment you will measure the potential difference across a resistor R2 of resistance R2 as the resistance of the circuit is varied. (a) (i) Connect the circuit shown in Fig. 1.1 using one of the resistors in the chain. V 4.5V X Y chain of resistors R2 Fig. 1.1 (ii) Record the value of the potential difference V across R2. V = …

4 9702/31/M/J/07 For Examiner’s Use © UCLES 2007 (b) Change the number n of resistors between X and Y and repeat (a)(ii) until you have six sets of readings for V and n. Include values of 1 / V in your table of results. (c) (i) Plot a graph of 1 / V (y-axis) against n (x-axis). (ii) Draw the line of best fit. (iii) Determine the gradient and the y-intercept of the graph. gradient = … y-intercept = …

5 9702/31/M/J/07 [Turn over For Examiner’s Use © UCLES 2007

6 9702/31/M/J/07 For Examiner’s Use © UCLES 2007 (d) V and n are related by the equation 1 nR1 1 –– = ––– + –– V ER2 E where R1 is the resistance of each of the resistors in the chain and E is the e.m.f. of the battery. Using your answers from (c)(iii), determine values of E and the ratio R1 –– R2 . You should include units where appropriate. E = … R1 –– R2 = …

7 9702/31/M/J/07 [Turn over For Examiner’s Use © UCLES 2007 You may not need to use all of the materials provided. 2 In this experiment you will investigate the height to which a ball rises when it has been released from a stretched piece of rubber. (a) (i) Suspend the piece of rubber from a clamp and stand using the two small blocks of wood. Attach the ball to the lower end of the rubber. The arrangement should be as shown in Fig. 2.1. blocks of wood piece of rubber ball Fig. 2.1 (ii) Clamp the rule vertically. Position the rule near to the suspended ball. (iii) Record the position of the centre of mass of the ball when it is in equilibrium. position of centre of mass of the ball = …

8 9702/31/M/J/07 For Examiner’s Use © UCLES 2007 (b) (i) Pull the ball vertically downwards. Record the new position of the centre of mass of the ball and determine its vertical displacement x. new position of centre of mass of the ball = … x = … (ii) Release the ball and note the position of its centre of mass when the ball reaches maximum height. position of centre of mass at maximum height = … (iii) Calculate the maximum height h of the ball above the equilibrium position. h = … (c) Estimate the percentage uncertainty in h, showing your working. percentage uncertainty in h = …

9 9702/31/M/J/07 [Turn over For Examiner’s Use © UCLES 2007 (d) Change the value of x and repeat (b). Record the new values of x and h. position of centre of mass when displaced = … position of centre of mass at maximum height = … x = … h = … (e) It is suggested that h is directly proportional to x 2. Do the results of your experiment support this idea? You should explain your reasoning clearly. … … … …

10 9702/31/M/J/07 For Examiner’s Use © UCLES 2007 (f) (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 9702/31/M/J/07 BLANK PAGE 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2007 question paper 9702 PHYSICS 9702/31 Paper 31 (Advanced Practical Skills), 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. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. 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 May/June 2007 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 31 © UCLES 2007 1 Manipulation, measurement and observation Successful collection of data (b) Measurements [6] One mark for each set of readings for V and n. (b) Apparatus set up without help from supervisor. [1] Range and distribution of values (c) n = 1 or 2 and n = 10 or 11 must be included and no more than a gap of three. [1] Quality of data (Graph) Judge by scatter of points about the best fit line. [1] At least 5 plots are needed on the trend line for this mark to be scored. Presentation of data and observations Table: layout (b) Column headings (V/V, 1/V / V -1 only). Ignore n column. [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. Table: raw data (b) Consistency of presentation of raw readings. [1] All values of V must be given to the same number of decimal places. Table: calculated quantities (b) Significant figures [1] Apply to 1/V. If V is given to 2 s.f., then accept 1/V to 2 or 3 s.f. If V is given to 3 s.f., then accept 1/V to 3 or 4 s.f. If V is given to 4 s.f., then accept 1/V to 4 or 5 s.f. (b) Values of 1/V correct. [1] Check a value. If incorrect, write in the correct value. Allow small rounding errors. Graph: layout (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 must occupy at least half the graph grid in both x and y directions. Indicate false origin with FO. Scales must be labelled with the quantity which is being plotted. Ignore units.

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 31 © UCLES 2007 Graph: plotting of points (Graph) All observations must be plotted. [1] Ring and check a suspect plot. Tick if correct. Re-plot if incorrect. Work to an accuracy of half a small square. Graph: trend line (Graph) Line of best fit (of 5 or 6) [1] Judge by scatter of points 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. Analysis, conclusions and evaluation Interpretation of graph (c) Gradient [1] The hypotenuse of the ∆ must be greater than half the length of the drawn line. Read-offs must be accurate to half a small square. Check for ∆y/∆x (i.e. do not allow ∆x/∆y). (c) y-intercept from graph or substitute correct read-offs into y = mx + c. [1] If a false origin has been used then label FO. Drawing conclusions (d) Value for E. [1] Expect between 4–5V. Should be 1/y-intercept. Check the value. Unit required. 2/3 s.f. (d) Value for R1/R2. [1] Expect 0.19–0.23 unless supervisor has used different resistors. Method of working must be correct. If a unit is given then this mark cannot be scored. 2/3 s.f. [Total: 20]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 31 © UCLES 2007 2 Manipulation, measurement and observation Successful collection of data (a) (iii) Position of centre of mass of ball at equilibrium [1] (Value < 1m and appropriate unit. No more than 1 d.p. in cm.) (b) (i) Position of centre of mass of ball when displaced [1] (ii) Position of centre of mass of ball at maximum height [1] (d) Second position of centre of mass of ball when displaced [1] (d) Second position of centre of mass of ball at maximum height [1] (b)/(d) Repeated measurements for maximum height [1] Quality of data (d) Bigger x gives bigger h [1] Presentation of data and observations Display of calculation and reasoning (b), (d) Values of x calculated correctly. (Displaced – equilibrium position) [1] Both values required. Unit need not be stated but must be consistent. Calculations must be checked. (b), (d) Values of h calculated correctly. (Max height – equilibrium position) [1] Both values required. Unit need not be stated but must be consistent. Calculations must be checked. (e) Correct calculation to check proportionality [1] Possibilities include: Two calculations of x2/h or ratio of x2 values and ratio of h values both calculated. Analysis, conclusions and evaluation Drawing conclusions (e) Conclusion [1] Sensible comments supported by calculations and suggested relation. Incorrect ideas score zero. Estimating uncertainties (c) (ii) Percentage uncertainty in h. [1] Uncertainty in h is 2–10 mm. Whole numbers only. If repeated readings have been done then the uncertainty could be half the range. Correct ratio idea required, ×100 stated/implied.

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 31 © UCLES 2007 Identifying limitations (f) (i) Relevant points must be underlined and ticked. [4] Some of these might be: A Ruler not vertical. B Locating the centre of the ball (when reading ruler). C Parallax error. D Establishing when the ball is at its maximum displacement. E Only two displacements (are not enough to validate the conclusion). F Difficulty in the release of the mass (reference to force/vertical plane). Suggesting improvements (f) (ii) Relevant points must be underlined and ticked. [4] Some of these might be: A Sensible method to ensure ruler vertical. B Place the rule as close as possible to the mass/mark the centre of the ball with mark or pointer/use the bottom/top of the ball. C Measure at eye level/repeat to get eye in the right place/place the rule as close as possible to the mass. D Use video camera (play back) frame by frame/slow motion/position sensor above or below. E Need a wider range of displacements and plot a graph/find mean k. F Use a clamp/electromagnet to release the mass. Do not allow ‘repeated readings’, ‘human error’. Do not allow ‘use a computer to improve the experiment’. [Total: 20]