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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2012 question paper for the…

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2012 question paper for the guidance of teachers 9702 PHYSICS 9702/31 Paper 3 (Advanced Practical Skills 1), 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. ã Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2012 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 AS/A LEVEL – May/June 2012 9702 31 1 (a) (iii) Value of x in the range 0.50 – 0.60 m. [1] (b) (ii) Value of T with unit: 0.9 s T 1.3 s. [1] Evidence of repeats. [1] (c) Six sets of readings of x and T scores 4 marks, five sets scores 3 marks etc. Incorrect trend –1. Minor help from Supervisor –1; major help –2. [4] Range of x at least 25 cm. [1] Column headings: Each column heading must contain a quantity and a unit where appropriate. [1] The unit must conform to accepted scientific convention e.g. x/m or x(m) or x in m. Consistency of presentation of raw readings: [1] All values of x must be given to the nearest mm. Significant figures: [1] Significant figures for √x should be the same as, or one more than, s.f. for x. Calculation: √x calculated correctly. [1] (d) (i) 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 on the grid occupy at least half the graph grid in both x and y directions. Scales must be labelled with the quantity that is being plotted. Scale markings should not be greater than three large squares apart. Plotting of points: [1] All the observations in the table must be plotted. Check the points are plotted correctly. Work to an accuracy of half a small square. Do not accept ‘blobs’ (points with diameter greater than half a small square). Quality: [1] All points in the table must be plotted (at least 5) for this mark to be scored. Judge by the scatter of all the points about a straight line. All points must be within 0.04 m½ (0.4 cm½) on the √x axis from a straight line. (ii) Line of best fit: [1] Judge by the balance of all the points on the grid (at least 5) about the candidate’s line. There must be an even distribution of points either side of the line along the full length. Allow one anomalous point if clearly indicated (e.g. circled or labelled) by the candidate. Line must not be kinked or thicker than half a small square. © University of Cambridge International Examinations 2012 Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9702 31 (iii) Gradient: [1] The hypotenuse of the triangle must be at least half the length of the drawn line. Both read-offs must be accurate to half a small square in both the x and y directions. Do not allow ∆x/∆y. y-intercept: [1] Either: Check correct read-off from a point on the line, and substitution into y = mx + c. Read- off must be accurate to half a small square in both the x and y directions. Allow ecf of gradient value. Or: Check the read-off of the intercept directly from the graph. (e) Value of P = candidate’s gradient and Q = value of candidate’s intercept. Do not allow fractions. [1] Unit for P (s m–½ or s cm–½ or s mm–½) consistent with value, and Q (s). [1] [Total: 20] 2 (a) (iii) Value of F0 with unit. [1] Evidence of repeats. [1] (iv) Absolute uncertainty in F0 in range 0.4 – 1 N. If repeated readings have been taken, then the uncertainty can be half the range. Correct method of calculation of percentage uncertainty. [1] (v) Value of µ given to 2 or 3 s.f. [1] (b) (ii) Value of θ with unit to the nearest degree. [1] (iii) Correct calculation of (sin θ + µ cos θ). [1] (c) (ii) Value of F. [1] (d) Second value of θ. [1] Second value of θ first value of θ. [1] Second value of F first value of F. [1] Allow F2 F1 if θ2 θ1. (e) (i) Correct calculation of two values of k. [1] (ii) Sensible comment relating to the calculated values of k, testing against a specified criterion. [1] © University of Cambridge International Examinations 2012 Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9702 31 (f) (i) Limitations 4 max. (ii) Improvements 4 max. No credit/not enough A two readings are not enough take more readings and plot few readings/ (to draw a conclusion) a graph/ take more readings and calculate more k values and calculate average k/ compare only one reading B some parts of board rougher method to ensure same board is rough/ than others/ section of board used in each there is friction between the surface of board is uneven/ experiment (e.g. mark one block and the board/ board not flat section) use a smoother surface/ references to oil/lubricants C large (percentage) uncertainty use larger/heavier masses values of F very similar in F D difficulty in arranging newton- use (long) piece of string to newton-meter touching board meter parallel to board/pulling connect the newton-meter to when attached in line with board the block E block moves suddenly/without use system of pulley and warning (so difficult to read weights/ sand to measure F/ newton-meter at the instant use a newton-meter with a the block starts to move) max hold facility/ use video and playback/ value of F changes when use force sensor and block moves datalogger/computer F board tends to slip/ method described to secure board not stable/ board/block/support e.g. supporting block can topple clamp the board, fix the supporting block to the bench with tape/blu-tack G cannot zero newton-meter use system of pulley and zero error in newton-meter when used horizontally weights/ sand to measure F/ use force sensor and datalogger/computer Ignore ‘parallax problems’, ‘use assistant’ or references to draughts, fans, a.c. [Total: 20] © University of Cambridge International Examinations 2012

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