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CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2012 series 9702 PHYSICS 9702/33…

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CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2012 series 9702 PHYSICS 9702/33 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 should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2012 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components. Page 2 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9702 33 1 (b) (i) Value of h in range 0.085 m Y h Y 0.095 m consistent with unit. [1] (c) Value of T in range 0.6 s Y T Y 1.5 s consistent with unit. [1] Evidence of repeats. [1] (d) Six sets of readings of h and T or raw times scores 4 marks, five sets scores 3 marks etc. Help from Supervisor –1. [4] Range: hmax – hmin [ 15.5 cm [1] Column headings: Each column heading must contain a quantity and a unit where appropriate. The unit must conform to accepted scientific convention e.g. T2h / s2m (or m s2) and h2/ m2. [1] Consistency: All raw values of h must be given to the nearest mm. [1] Significant figures: All values of h2 must have the same number of significant figures as, or one more than, the number of significant figures in h. [1] Calculation: Values of T2h calculated correctly. [1] (e) (i) Axes: [1] Sensible scales must be used, no awkward scales (e.g. 3:10). 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 that is being plotted. Scale markings must be no more than three large squares apart. Plotting of points: [1] All observations in the table must be plotted on the graph grid. Diameter of plots must be Y half a small square (no “blobs”). Check that the points are plotted correctly. Work to an accuracy of half a small square in both the x and y directions. 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 ± 0.0025 m2 (25 cm2) in the h2 direction of a straight line. (ii) Line of best fit: [1] Judge by 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 only if clearly indicated (i.e. circled or labelled) by the candidate. Line must not be kinked or thicker than half a small square. © Cambridge International Examinations 2012 Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9702 33 (iii) Gradient: [1] The sign of the gradient must match the graph. The hypotenuse of the triangle should be greater than 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. The method of calculation must be correct. y intercept: [1] Either: 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. Or: Correct read-off of the intercept directly from the graph. (f) Value of P = candidate’s gradient. Value of Q = candidate’s intercept. [1] Do not allow a value presented as a fraction. Unit for P (s2 m–1 or s2 cm–1 or s2 mm–1) and Q (s2 m or s2 cm or s2 mm) correct and [1] consistent with value. [Total: 20] 2 (a) (ii) Value of L in range: 5.0 cm Y L Y 15.0 cm with unit to nearest mm. [1] (b) (ii) Value of s in range: 50.0 cm Y s Y 70.0 cm with unit. [1] Supervisor’s help –1. Evidence of repeat measurements. [1] (iii) Absolute uncertainty in s is between 2 cm – 10 cm. [1] If repeated readings have been taken, then the absolute uncertainty can be half the range. Correct method used to calculate the percentage uncertainty. (iv) Correct calculation of x. [1] (c) Raw value(s) of t greater than 1 s to a precision of 0.1 or 0.01 s with unit. [1] (d) (i) Correct calculation of v using either value of x with consistent unit. [1] (ii) Justification of significant figures in v linked to significant figures in t and x or (s – L) (not just “raw readings”). [1] (e) (iii) Second value of t. [1] Second value of s. [1] Quality: correct trend; If s increases, t increases. [1] (f) Sensible comment relating to the calculated values of v, testing against a criterion specified by the candidate. [1] © Cambridge International Examinations 2012 Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9702 33 (g) (i) Limitations 4 max. (ii) Improvements 4 max. Do not credit A two readings not enough (to draw take many readings (for different ‘repeat readings’ a conclusion) masses) and plot a graph /few readings /calculate more v values and /take more compare readings and calculate average v B the car does not travel in a method of determining the distance straight line e.g. video + scale/method of marking a path /method of guiding trolley in straight line C times are short use a longer slope trolley too fast /large uncertainty in t /use a steeper slope D difficult to judge when trolley improved method of timing eg light gate(s) stopped/ video with timer or frame by /reaction time difficult to start the stopwatch frame/motion sensor placed at end /human error when all wheels on bench/when of path/ticker tape timer trolley at B/when trolley horizontal E there is a drop when the trolley method to smooth transition e.g. reaches the end of the board/at B thinner board/bevelled edge/thin there is a loss of velocity/kinetic card placed at transition energy F difficult to release without method of releasing trolley e.g. air resistance applying a force/ velocity card/barrier or electromagnet /difficult to position head at B after releasing trolley A G calculation of x doesn’t take back detailed method of measuring from measuring l of trolley into account wheel to the back of the trolley [Total: 20] © Cambridge International Examinations 2012

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