Cambridge A Level Physics 9702 — 2009 Oct/Nov Paper 5 · Variant 2

This document consists of 8 printed pages. DC (SHW 00379 1/09) 17453/3 © UCLES 2009 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education 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 all questions. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. * 3 2 3 2 6 1 1 1 7 7 * PHYSICS 9702/52 Paper 5 Planning, Analysis and Evaluation October/November 2009 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. For Examiner’s Use 1 2 Total

2 9702/52/O/N/09 © UCLES 2009 For Examiner’s Use 1 When a current passes through a wire, the wire becomes hot and expands. This can be investigated in a laboratory by passing a current through a wire of diameter d and measuring the displacement y, as shown in Fig. 1.1. to circuit thin wire y wire when current passes Fig. 1.1 It is suggested that the diameter d of the wire is related to y by the equation y = pd q where p and q are constants. Design a laboratory experiment to investigate the relationship between d and y, so as to determine a value for q. You should draw a diagram showing the arrangement of your equipment. In your account you should pay particular attention to (a) the procedure to be followed, (b) the measurements to be taken, (c) the control of variables, (d) the analysis of the data, (e) the safety precautions to be taken. [15]

3 9702/52/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use Diagram … … … … … … … … … … … … … …

4 9702/52/O/N/09 © UCLES 2009 For Examiner’s Use … … … … … … … … … … … … … … … … … … … … … … … … … … …

5 9702/52/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use 2 An experiment is carried out to investigate how the time t for a steel ball to fall through air varies with the height h through which it falls. The equipment is set up as shown in Fig. 2.1. electromagnet steel ball light gates h to start timer to stop timer Fig. 2.1 An electromagnet is used to release the ball. As soon as the ball is released, it passes a light gate, which starts a timer. As the ball passes the lower light gate, the timer is stopped. Question 2 continues on the next page.

6 9702/52/O/N/09 © UCLES 2009 For Examiner’s Use It is suggested that t and h are related by the equation h = 1 2gt 2 where g is the acceleration of free fall. (a) A graph is plotted with t 2 on the y-axis and h on the x-axis. Express the gradient in terms of g. gradient = … [1] (b) Values of h and t are given in Fig. 2.2. h / m t / s 0.60 0.35 ± 0.01 0.75 0.39 ± 0.01 0.90 0.43 ± 0.01 1.00 0.45 ± 0.01 1.15 0.49 ± 0.01 1.30 0.52 ± 0.01 Fig. 2.2 Calculate and record values of t 2 in Fig. 2.2. Include the absolute uncertainties. [3] (c) (i) Plot a graph of t 2 / s2 against h / m. Include error bars for t 2. [2] (ii) Draw the straight line of best fit and a worst acceptable straight line on your graph. Both lines should be clearly labelled. [2] (iii) Determine the gradient of the line of best fit. Include the uncertainty in your answer. gradient = … [2]

7 9702/52/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use 0.10 0.60 h / m t 2 / s2 0.70 0.80 0.90 1.00 1.10 1.20 1.30 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30

8 9702/52/O/N/09 © UCLES 2009 For Examiner’s Use (d) Using your answer to (c)(iii), determine the value of g. Include the absolute uncertainty in your value and an appropriate unit. g = … [3] (e) The experiment is repeated from the top of a building. (i) The time taken for the steel ball to fall is 2.21 ± 0.01 s. Using your value of g, calculate the height b of the building. b = … m [1] (ii) Determine the percentage uncertainty in b. percentage uncertainty = … % [1] 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 October/November 2009 question paper for the guidance of teachers 9702 PHYSICS 9702/52 Paper 52 (Planning, Analysis and Evaluation), maximum raw mark 30 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 52 © UCLES 2009 Question 1 Planning (15 marks) Defining the problem (3 marks) P1 Vary d and measure y or d is the independent variable and y is the dependent variable [1] P2 Keep current constant [1] P3 Keep length of wire constant [1] Methods of data collection (5 marks) M1 Diagram showing ruler positioned and power supply connected to wire or diagram showing initial and final marks on screen and power supply connected to wire [1] M2 Use of ammeter to check current – penalise incorrect circuit diagrams [1] M3 Measurement of d using micrometer [1] M4 Allow time for displacement of wire to stabilise [1] M5 Detail on measuring y; final reading - initial reading [1] Method of analysis (2 marks) A1 Plot a graph of log y against log d [1] A2 q = gradient [1] Safety considerations (1 mark) S Safety related to hot wire – use of gloves, wait to cool down/switch off before changing wire, do not touch hot wire [1] Additional detail (4 marks) D Relevant points might include [4] 1. Use of vernier scale to measure y /well described optical method/use of set square 2. Method for keeping current constant e.g. use of rheostat 3. Check starting position for y for same wire 4. lg y = q lg d + lg p 5. Repeat measurements of d at different points along the wire and determine average 6. Control of additional variables e.g. separation between supports, room temperature 7. Use of protective resistor (either labelled or explained). 15 marks can be scored in total.

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 52 © UCLES 2009 Question 2 Analysis, conclusions and evaluation (15 marks) Part Mark Expected Answer Additional Guidance (a) A1 g 2 (b) T1 t2 / s2 Column heading: allow t2 (s2) or t2in s2 Do not allow (t / s)2 T2 0.12 or 0.123 0.15 or 0.152 0.18 or 0.185 0.20 or 0.203 0.24 or 0.240 0.27 0r 0.270 Must be to two or three significant figures. A mixture of 2sf and 3sf is allowed. U1 ± 0.007 to ± 0.010 (allow ± 0.011) Allow more than one significant figure. (c) (i) G1 Six points plotted correctly. Must be within half a small square. Use transparency. Ecf allowed from table. U2 Error bars in t2 plotted correctly. Check first and last point. Must be accurate within half a small square. (c) (ii) G2 Line of best fit. If points are plotted correctly then lower end of line should pass between (0.60, 0.116) and (0.60, 0.123) and upper end of line should pass between (1.30, 0.268) and (1.30, 0.272). Allow ecf from points plotted incorrectly – examiner judgement. Five good trend plots needed. G3 Worst acceptable straight line. Steepest or shallowest possible line that passes through all the error bars. Line should be clearly labelled or dashed. Should pass from top of top error bar to bottom of bottom error bar or bottom of top error bar to top of bottom error bar. Mark scored only if error bars are plotted. (c) (iii) C1 Gradient of best fit line. The triangle used should be greater than half the length of the drawn line. Check the read offs. If incorrect circle and write in correct value. Work to half a small square. Do not penalise POT. U3 Uncertainty in gradient. Method of determining absolute error Difference in worst gradient and gradient. (d) C2 g = 2/gradient Gradient must be used. Allow ecf from (c) (iii) U4 Method of determining uncertainty in g. Uses worst gradient and finds difference. Allow fractional error methods. Do not check calculation.

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9702 52 © UCLES 2009 C3 Unit of g: m s-2 Accept N kg-1 (e) (i) C4 21.9 – 23.5 Answer must be in range given to 2 or 3sf. Allow 22 or 23. (e) (ii) U5 Method for percentage uncertainty in b. Calculates percentage uncertainty in t2 and adds to percentage uncertainty in gradient or g. Allow ecf from (c) (iii) and/or (d). [Total: 15] Uncertainties in Question 2 (c) (iii) Gradient [U3] 1. Uncertainty = gradient of line of best fit – gradient of worst acceptable line 2. Uncertainty = ½ (steepest worst line gradient – shallowest worst line gradient) (d) g [U4] 1. Uncertainty = g from gradient - g from worst acceptable line 2. gradient gradient g g ∆ ∆ = (e) b [U5] 1. Substitution method to find worst acceptable g using either largest g × 2.222 or smallest g × 2.202 then determines percentage uncertainty 2. 0.9% + percentage uncertainty in gradient or percentage uncertainty in g 3. 100 2 100 ×       ∆ + ∆ = × ∆ t t g g b b