Physics 9702/34 May/June 2020: question paper and mark scheme

Mark scheme

1(a) Value of d in range 14.0–16.0 cm. 1 1(b) Value of t in range 10.00–20.00 s. 1 Evidence of repeated readings of t. 1 1(c) Six sets of readings of d and T showing the correct trend and without help from the Supervisor scores 4 marks, five sets 4 scores 3 marks etc. Range: dmin ⩽ 10.0 cm and dmax ⩾ 20.0 cm. 1 Column headings: 1 Each column heading must contain a quantity, a unit and a separating mark where appropriate. The presentation of quantity and unit must conform to accepted scientific convention. e.g. 1 / d / cm–1 Consistency: 1 All values of d must be given to the nearest 0.1 cm. Significant figures: 1 Number of significant figures for every value of 1 / d the same as, or one more than, the number of s.f. of d as recorded in table. Calculation: 1 Values of 1 / d calculated correctly. 1(d)(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 should be no more than three large squares apart. Plotting of points: 1 All observations in the table must be plotted on the grid. Diameter of plotted points must be ⩽ half a small square. Points must be plotted to an accuracy of half a small square. 1(d)(i) Quality: 1 All observations in the table (at least 5) must be plotted on the grid. Trend of points must be correct. It must be possible to draw a straight line that is within ± 20 s2 in the t 2 direction of all plotted points. 1(d)(ii) Line of best fit: 1 Judge by 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 curve along the full length. If there are 6 or more points, allow one anomalous point only if clearly indicated by the candidate. Line must not be kinked or thicker than half a small square. 1(d)(iii) Gradient: 1 The hypotenuse of the triangle used must be greater than half the length of the drawn line. The method of calculation must be correct. Do not allow Δx / Δy. Both read-offs must be accurate to half a small square in both the x and y directions. y-intercept: 1 Correct read-off from a point on the line and substituted into y = mx + c. 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 1 / d = 0 accurate to half a small square. 1(e) Value of a equal to candidate’s gradient and value of b equal to candidate’s intercept. 1 The values must not be fractions. Correct units for a (e.g. cm s2) and b (s2). 1

Mark scheme

2(a)(i) Value of T in the range 0.50–1.00 s. 1 2(a)(ii) Correct calculation of k. 1 2(b) Value of y to nearest 0.001 m and in range 0.050–0.150 m. 1 2(c) Value for H. 1 Evidence of repeated readings of H. 1 2(d) Percentage uncertainty in H based on an absolute uncertainty of 4–8 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(e) Second values of y and H. 1 Quality: second H < first H. 1 2(f)(i) Two values of c calculated correctly and both values given to two or more significant figures. 1 2(f)(ii) Justification based on significant figures in H and y. 1 2(f)(iii) Valid comment consistent with calculated values of c, testing against a criterion stated by the candidate. 1 2(g) Correct calculation of g, with unit. 1 2(h)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”). 4 B Mass oscillates horizontally as well as vertically. C y varies around the masses/other specific problem with y. D Difficult to judge end points of oscillation. E H decreases with time/oscillations damped. F Parallax error when taking measurements for H. G Difficult to raise masses to same position for repeats. 1 mark for each point up to a maximum of 4. 2(h)(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 Valid method of restricting oscillation to vertical direction e.g. a guide. C Take several readings and average/clamp ruler vertically to measure y. D Video with rule in view and play back. E Use ‘peak-hold’ indicator to indicate maximum and minimum/use data logger with position sensor under mass hanger. F Hold rule in a clamp/other valid method to reduce parallax. G Use a stop e.g. horizontal piece of wood held by clamp. 1 mark for each point up to a maximum of 4.