Physics 9702/31 October/November 2019: question paper and mark scheme

Mark scheme

1(a) Value of V < 2.0 V with unit. 1 1(b) Value of d with unit and in the range 20.0–90.0 cm. 1 1(c) Six sets of readings of R and d (different values) showing the correct trend and without assistance from the Supervisor scores 5 5 marks, five sets scores 4 marks etc. Range: Values of R must include 12 Ω and 39 Ω. 1 Column headings: 1 Each column heading must contain a quantity and a unit where appropriate. The presentation of quantity and unit must conform to accepted scientific convention e.g. d / m and R / Ω and R / d / Ω m–1. Consistency: All values of d must be given to the nearest mm. 1 Significant figures: All values of R / d must be given to either 2 or 3 s.f. 1 Calculation: Values of R / d are correct. 1 1(d)(i) Axes: 1 Sensible scales are 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 should be no more than three large squares apart. Plotting of points: 1 All observations must be plotted on the grid. Diameter of plotted point must be ⩽ half a small square. Points must be plotted to an accuracy of half a small square. Quality: 1 All points in the table (at least 5) must be plotted on the grid for this mark to be awarded. Trend of points on graph must be positive. All points must be within 2.5 Ω on the R-axis of a straight line. 1(d)(ii) Line of best fit: 1 Judge by the balance of all 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 its full length. One anomalous point is allowed only if clearly indicated (i.e. circled or labelled) by the candidate. There must be at least 5 points left after the anomalous point is disregarded. Line must not be kinked or thicker than half a square. 1(d)(iii) Gradient: 1 The hypotenuse of the triangle used 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 sign of the gradient on the answer line must match the graph. Method of calculation must be correct, e.g. not ∆x / ∆y. y-intercept: 1 Correct read-off from a point on the line substituted into y = mx + c or an equivalent expression. Read-off must be accurate to half a small square in both x and y directions. or Intercept read directly from the graph, with read-off at R = 0, accurate to half a small square in the R direction. 1(e) Value of A = candidate’s gradient and value of B = candidate’s intercept. 1 The values must not be fractions. Unit for A is correct (e.g. m–1 or cm–1 or mm–1) and unit for B is correct (e.g. Ω m–1 or Ω cm–1 or Ω mm–1). 1

Mark scheme

2(a)(i) Value of x to the nearest mm with unit in the range 9.0–11.0 cm. 1 2(a)(ii) Percentage uncertainty in x based on absolute uncertainty of 2–4 mm. 1 If repeated readings have been taken, then the uncertainty can be half the range (but not zero) if the working is clearly shown. Correct method of calculation to obtain percentage uncertainty. 2(b)(i) Value of raw L to the nearest mm with unit and in the range 20.0–30.0 cm. 1 2(b)(ii) Correct calculation of L. 1 2(b)(iii) Justification for s.f. in L linked to s.f. in L. 1 2(c) Second value of x. 1 Second value of L. 1 Quality: Second value of L > first value of L. 1 2(d)(i) Two values of k calculated correctly. 1 2(d)(ii) Valid comment consistent with calculated values of k, testing against a criterion stated by the candidate. 1 2(e)(i) Value of T in the range 1.0–2.0 s. 1 2(e)(ii) Correct calculation of g with correct consistent unit using second value of k. 1 2(f)(i) A Too few readings/(only) two readings not enough to draw a (valid) conclusion (not ‘not enough for accurate results’, ‘few 4 readings’). B Difficult to determine x or L0 or L with reason e.g. parallax error/locating centre of bob/lower curved edge of wooden rod/holding ruler by hand. C Difficult to release two bobs at same instant/time. D Pendulums have different amplitudes/displacements or Two oscillations have different motions so difficult to compare. E Difficult to judge when the two pendulums are exactly in phase/difficult to adjust to the exact length so that the pendulums are in phase/trial and error process needed to identify when length gives same phase. F Difficult to judge start of/end of/complete oscillation. 1 mark for each point up to a maximum of 4. 2(f)(ii) A Take more readings and plot a graph or take more readings and compare k values (not ‘repeat readings’ on its own). 4 B Measure to top and bottom of ball and take average or Take string off and measure on table or Clamp a ruler (vertically). C Improved method of release e.g. card gate release. E Use stop-watch and test for same period for each pendulum. F Video/record/film and view with timer/frame-by-frame. 1 mark for each point up to a maximum of 4. There is no marking point labelled D.