Physics 9702/34 October/November 2019: question paper and mark scheme

Mark scheme

1(a) Value of x in range 13.0–17.0 cm. 1 1(b) Evidence of repeat readings of nT with n ⩾ 5. 1 1(c) Six sets of readings of x and time with correct trend and without help from the Supervisor scores 4 marks, five sets scores 4 3 marks, etc. Range: xmin ⩽ 5.0 cm and xmax ⩾ 20.0 cm. 1 Column headings: 1 Each column heading must contain a quantity, a unit and a separating mark. The presentation of quantity and unit must conform to accepted scientific convention. e.g. T2 / s2. Consistency: All values of x must be given to the nearest 0.1 cm. 1 Significant figures: 1 All values of x2 must be given to the same number of s.f. as, or one greater than, the number of s.f. of x as recorded in the table. Calculation: Values of T2 calculated correctly. 1 1(d)(i) Axes: 1 Sensible scales must be used, no awkward scales (e.g. 3:10 or fractions). Scales must be chosen so that the points plotted 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 be no more than three large squares apart. Plotting of points: 1 All observations 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 in both x and y directions. Quality: 1 All points in the table must be plotted (at least 5). Trend of points on graph must be positive. Scatter of points must be no more than ±25 cm2 (to scale) from a straight line in the x2 direction. 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 must be greater than half the length of the drawn line. Method of calculation must be correct, e.g. not ∆x / ∆y. 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 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 x = 0 accurate to half a small square in the y direction. 1(e) a equal to candidate’s gradient and b equal to candidate’s intercept. 1 The values must not be fractions. Unit for a is correct (e.g. s2 m–2) and unit for b is correct (s2). 1 1(f) Value for g calculated correctly. 1

Mark scheme

2(a) Value for h to nearest mm and in range 7–13 mm. 1 2(b) Value for W to nearest 0.1 N and in the range 1.0 N ⩽W ⩽ 5.0 N. 1 2(c)(i) Evidence that d has been measured to find r. 1 2(c)(ii) Correct calculation of α. 1 2(c)(iii) Justification based on s.f. in (r – h) and r. 1 2(d) Raw values for F to nearest 0.1 N with unit. 1 Evidence of repeat readings of F. 1 2(e) Percentage uncertainty based on an absolute uncertainty in F of 0.1–0.4 N. 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(f) Values for second W, r and F. 1 Quality: Second F less than first F. 1 2(g)(i) Two values of k calculated correctly. 1 2(g)(ii) Valid comment relating to the calculated values of k, testing against a criterion specified by the candidate. 1 2(h)(i) A Too few readings/(only) two readings not enough to draw a (valid) conclusion (not ‘not enough for accurate results’, 4 ‘few readings’). B Large percentage uncertainty in h or h is small so large uncertainty in h. C Difficult to measure diameter with reason, e.g. because diameter not clearly defined, edge is tapered. D Difficult to measure F/read newton meter with a reason, e.g. difficult to judge moment when cylinder starts to roll/cylinder moves suddenly/non-zero reading on newton meter when horizontal. E Force applied at different angles for each cylinder/difficult to pull newton meter horizontally. F Large percentage uncertainty in F or values of F small so large uncertainty in F. 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 Use vernier/digital calipers or micrometer. C Improved method of measuring diameter, e.g. measure between set squares/put blocks either side and measure between blocks. D Use system of pulley and weights/sand or Pointer/marker that stays in maximum position on newton mete/use force sensor and data-logger or Video/film/record experiment with newton meter in view. E Method of applying force horizontally, e.g. use longer loop of thread/support newton meter with additional board. F Use e.g. 0–5 N newton meter (not ‘more accurate meter’). 1 mark for each point up to a maximum of 4.