Cambridge A Level Physics 9702 — 2007 Oct/Nov Paper 3 · Variant 2

This document consists of 9 printed pages and 3 blank pages. SP (SLM/CG) T26893/2 © UCLES 2007 [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. * 8 8 7 0 7 4 5 8 6 8 * PHYSICS 9702/32 Paper 32 Advanced Practical Skills 2 October/November 2007 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/07 [Turn over For Examiner’s Use © UCLES 2007 1 In this experiment, you will determine the resistance of an unknown resistor R1. (a) A wire XY has been taped to a metre rule. Connections to this wire may be made using crocodile clips. (i) Connect the circuit shown in Fig. 1.1. R1 has been labelled. R2 may be made using any series or parallel combination of the remaining resistors. These resistors may be connected to each other by twisting the resistor wires together. R1 R2 l X Y S A Fig. 1.1 (ii) Position the sliding contact S on the wire and adjust the position of the contact until the reading on the meter is zero. Record the length l in centimetres from X to S. l = …cm

4 9702/32/O/N/07 For Examiner’s Use © UCLES 2007 (b) Change the value of the resistance R2 of the resistor R2 and repeat (a)(ii) until you have six sets of readings for l and R2. Values of l should be given in centimetres. Include values of 1 l in your table of results. When you have finished making measurements, disconnect the battery. (c) (i) Plot a graph of 1 l (y-axis) against R2 (x-axis). (ii) Draw the line of best fit. (iii) Determine the gradient and the y-intercept of the graph. gradient = … y-intercept = …

5 9702/32/O/N/07 [Turn over For Examiner’s Use © UCLES 2007

6 9702/32/O/N/07 For Examiner’s Use © UCLES 2007 (d) The relationship between l and R2 is 1 l = R2 LR1 + k where R1 is the resistance of the resistor R1, L = 100 cm and k is a constant. Using your answers from (c)(iii), determine values of R1 and k. Include appropriate units in each case. R1 = … k = …

7 9702/32/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 2 When an object falls in air, it experiences a drag force which opposes the motion of the object. Larger objects experience greater drag forces. In this experiment, you will investigate how the terminal velocity of a paper cone falling in air depends on the diameter of the cone. (a) Cut a sector out of a piece of filter paper as shown in Fig. 2.1. Fig. 2.1 (b) (i) Tape the straight edges of the paper together to produce a cone, as shown in Fig. 2.2. d Fig. 2.2 (ii) Measure and record the diameter d of the cone. d = …cm

8 9702/32/O/N/07 For Examiner’s Use © UCLES 2007 (c) (i) Mount a metre rule vertically using a stand, boss and clamp. (ii) Release the cone from a short distance above the top of the metre rule, as shown in Fig. 2.3. paper cone Fig. 2.3 Make and record measurements to determine the time t for the cone to fall through a distance h from the top of the metre rule. h = …cm t = …s (d) Estimate the percentage uncertainty in t, showing your working. percentage uncertainty in t = … (e) Calculate the terminal velocity v of the cone. v = …cm s–1

9 9702/32/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 (f) (i) Remove the tape from the paper and cut away a larger sector as shown in Fig. 2.4. Fig. 2.4 (ii) Repeat (b), (c)(ii) and (e), recording your results below. d = …cm h = …cm t = …s v = …cm s–1 (g) It is suggested that v is inversely proportional to d. Do the results of your experiment support this suggestion? Explain your reasoning clearly. … … … …

10 9702/32/O/N/07 For Examiner’s Use © UCLES 2007 (h) (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/07 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 2007 question paper 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. 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 October/November 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 – October/November 2007 9702 32 © UCLES 2007 Question 1 Manipulation, measurement and observation Successful collection of data (b) Measurements [5] Five marks for six sets of readings for l and R2, four for five sets, etc. (–1 for unreasonable values of R2, e.g. R2>40 or R2<2.5, e.g. impossible R2) (b) Circuit set up without help from Supervisor (minor help –1, major help –2) [2] Range and distribution of values (b) R2 values must include 40 Ω and one value Y 5 Ω [1] Presentation of data and observations Table: layout (b) 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, l (cm)). Table: raw data (b) Consistency of presentation of raw readings [1] All values of l must be given to the same number of decimal places. (l can be to nearest 1 mm or 1 cm). Table: calculated quantities (b) Significant figures [1] Apply to 1/l only. If l is given to 2 sf, then accept 1/l to 2 or 3 sf. If l is given to 3 sf, then accept 1/l to 3 or 4 sf. Values of 1/l given as fractions lose this mark. (b) Values of 1/l correct. [1] Check a value. If incorrect, write in the correct value. Allow values of 1/l given as fractions for this mark. Graph: layout (Graph) Axes [1] Sensible scales must be used. Awkward scales (e.g. 3:10) are not allowed. There should not be more than three large squares between axis labels. Scales must be chosen so that the plotted points must occupy at least half the graph grid in both x and y directions. Scales must be labelled with the quantity which is being plotted (do not accept R instead of R2). Ignore units. Do not penalise reversed axes but penalise if the wrong graph has been plotted.

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 32 © 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 (and re-check quality mark). Work to an accuracy of half a small square. Penalise blobs [ half a small square diameter. Graph: trend line (Graph) Line of best fit (must be 5 or more plots, do not allow if scatter is large). [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. Quality of data (Graph) Judge by scatter of points about the best fit line (all points ±1 Ω) [1] Trend must be correct. At least 5 plots are needed for this mark to be scored. Analysis, conclusions and evaluation Interpretation of graph (c) (iii) Gradient [1] The hypotenuse must be at least half the length of the drawn line. Read-offs must be accurate to half a small square (if incorrect, write in correct value). Check for ∆y/∆x (i.e. do not allow ∆x/∆y). Ignore POTE. (c) (iii) y-intercept [1] The value must be read to the nearest half square. The value can be calculated using ratios or y = mx + c (if algebra is not obviously wrong). If a false origin has been used then label FO. Drawing conclusions (d) Value for R1 [1] There should be evidence that it is obtained from 1/(100cm x gradient). Must be in range 5 to 15 Ω. 2 or 3 sf. Unit required. (d) Value for k [1] Should be candidate’s intercept. 2 or 3 sf. Unit required. Should be in range 0.0050 to 0.0150 cm–1. [Total for Question 1: 20]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 32 © UCLES 2007 Question 2 Manipulation, measurement and observation Successful collection of data (b) (ii) First value of d to nearest cm or mm. [1] (c) (ii) First value of t (must be between 0.1 and 10 s). [1] (f) (ii) Second value of d (must be less than first value) [1] (f) (ii) Second value of t. [1] (f) (ii) Two values of h in range 0 to 130 cm. (both values could be the same) [1] (f) (ii) Repeated measurements for t (first or second reading) [1] Quality of data (f) (ii) Smaller d gives greater v (use corrected values of v). [1] Presentation of data and observations Display of calculation and reasoning (e) First value of v calculated correctly. Calculations must be checked (if wrong, write in correct value). [1] (f) (ii) Second value of v calculated correctly. Calculations must be checked (if wrong, write in correct value). [1] (g) Correct calculation to check proportionality [1] Possibilities include: Two calculations of vd. Ratio of v values and inverse ratio of d values both calculated.

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 32 © UCLES 2007 Analysis, conclusions and evaluation Drawing conclusions (g) Conclusion [1] Sensible comments relating to proportionality calculations and to the suggested relation. Incorrect ideas score zero. Estimating uncertainties (d) Percentage uncertainty in t. [1] Absolute uncertainty must be 0.1 to 0.5 s, or if repeated readings have been done then the uncertainty could be half the range. Correct ratio idea and x100 required. Identifying limitations (h) (i) Relevant points must be underlined and ticked. [4] Some of these might be: A Two sets of readings not enough (to draw valid conclusion). B Cone may have not reached terminal velocity. C Hard to see when cone strikes floor. D Cone falls at an angle (due to draughts/imbalance of cone). E Human error in timing/reaction time. F Difficult to measure diameter because cone flexible. G Parallax error (at reading positions). X Other source of error Suggesting improvements (h) (ii) Relevant points must be underlined and ticked. [4] Some of these might be: A Take more readings and plot a graph/calculate ratios. B Ensure terminal velocity by increasing release height/measure velocity at two intervals to check terminal velocity reached. C Use pressure/other sensor (on floor) to stop timer/use assistant to judge when it reaches the floor. D Turn off fans/balance the cone e.g. extra strip of tape. E1 Use light gate to trigger stopwatch/use video camera with slow motion replay/use multiflash photography/use high speed camera with known time intervals. E2 Time over greater distance. F Measure diameter of cone in two directions and average. G Drop in front of rule/read at eye level. Y Another improvement, well explained. Do not allow ‘repeated readings’ (unless qualified by ‘plot a graph’). Do not allow ‘use a computer to improve the experiment’ [Total for Question 2: 20]