Cambridge A Level Physics 9702 — 2013 May/June Paper 3 · Variant 4

1 In this experiment, you will investigate how a force acting on a pivoted wooden strip changes as the pivot position is moved. (a) (i) Assemble the apparatus as shown in Fig. 1.1 with the nail through the central hole in the wooden strip. d nail held in boss wooden strip string loop string loop M newton-meter mass stand string loop large mass L bench Fig. 1.1 (ii) Adjust the nail height so that the wooden strip is parallel to the bench. Adjust the position of the stand or the large mass so that the newton-meter is vertical. (b) (i) Measure and record the distance d from the nail to the string loop attached to the newton-meter, as shown in Fig. 1.1. d = .................................................. [1] (ii) Record the force F indicated by the newton-meter. F = .................................................... N (c) Reposition the strip with the nail through different holes and repeat (a)(ii) and (b) until For you have six sets of values of d and F. Examiner’s 1 Use Include values of in your table. d Do not use holes that result in a force outside the range of the newton-meter. [11] 1 (d) (i) Plot a graph of F on the y-axis against on the x-axis. [3] d (ii) Draw the straight line of best fit. [1] (iii) Determine the gradient and y-intercept of this line. gradient = ....................................................... y-intercept = ....................................................... [2] For Examiner’s Use (e) The quantities F and d are related by the equation For Examiner’s a Use F = + b d where a and b are constants. Using your answers from (d)(iii), determine the values of a and b. Give appropriate units. a = ....................................................... b = ....................................................... [2] You may not need to use all of the materials provided. For Examiner’s Use

Mark scheme: 1 (b) (i) Value of d in the range 0.480 – 0.500 m, with unit. [1] (c) Six sets of readings of d and F scores 6 marks, five sets scores 5 marks etc. [6] Incorrect trend or no d data –1. Minor help from Supervisor –1, major help –2. Range: dmax – dmin ≥ 30 cm. [1] Column headings: [1] Each column heading must contain a quantity and a unit. The presentation of quantity and unit must conform to accepted scientific convention e.g. 1/d / m–1. Consistency: [1] All values of d must be given to the nearest mm and all values of F must be given to the nearest 0.1 N. Significant figures: [1] Significant figures for every row of values of 1 / d same as, or one greater than, d as recorded in table. Calculation: [1] Values of 1 / d calculated correctly. (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. Points must be plotted to an accuracy of half a small square. Diameter of plotted points must be ≤ half a small square (no blobs). Quality: [1] All points in the table must be plotted on the grid (at least 5) for this mark to be awarded. Judge by the scatter of all the points about a straight line. Scatter of points must be less than ± 0.001 cm–1 from a straight line in the 1/d direction. (ii) Line of best fit: [1] Judge by balance of all the points on the grid about the candidate’s line (at least 5 points). There must be an even distribution of points either side of the line along the full length. One anomalous point is allowed only if clearly indicated (i.e. circled or labelled) by the candidate. Line must not be kinked or thicker than half a square. GCE AS/A LEVEL – May/June 2013 9702 34 (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. The method of calculation must be correct. y-intercept: [1] Either: Correct read-off from a point on the line substituted into y = mx + c or an equivalent expression, with read-off accurate to half a small square in both x and y directions. Or: Intercept read directly from the graph, with read-off accurate to half a small square in both x and y directions. (e) Value of a = candidate’s gradient. Value of b = candidate’s intercept. [1] Unit for a correct and consistent with value, e.g. N cm. Unit for b is correct and consistent with value, e.g. N. [1] [Total: 20]

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2 In this experiment, you will investigate how the speed of water flowing through a tube depends on the tube length. (a) (i) Take measurements to determine the internal diameter D of the flexible tube, as shown in Fig. 2.1. D Fig. 2.1 D = ............................................ cm [2] (ii) Estimate the percentage uncertainty in your value of D. percentage uncertainty = .................................................. [1] (b) Remove the plunger from the syringe body. (c) (i) Measure the length l of the flexible tube. l = ................................................. [1] (ii) Push the nozzle of the syringe body securely into one end of the flexible tube and then assemble the apparatus as shown in Fig. 2.2. Attach enough modelling clay near the bottom of the tube to make it hang vertically. clamp syringe body nozzle flexible tube stand modelling clay tray bench Fig. 2.2 (iii) Fill the syringe body to the top with water. For As the water level falls in the syringe body, take measurements to find the time t Examiner’s for the level to fall from the 40 cm3 graduation to the 10 cm3 graduation. (Note that Use 1 ml = 1 cm3.) t = ............................................... s [1] (iv) Calculate the average speed v of the water in the tube using the relationship 120 v = . π D2 t v = ...................................... cm s−1 [1] (d) Justify the number of significant figures that you have given for your value of v. .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [1] (e) (i) Detach the tube from the syringe body and reduce its length by cutting it in half. (ii) Repeat (c) with one of the shorter tubes. l = ....................................................... t = ..................................................... s v = ............................................ cm s−1 [3] (f) It is suggested that the relationship between v and l is For Examiner’s v2 = k l Use where k is a constant. (i) Using your data, calculate two values of k. first value of k = ....................................................... second value of k = ....................................................... [1] (ii) Explain whether your results support the suggested relationship. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [1]

Mark scheme: 2 (a) (i) All values of D to nearest 0.01 cm or all to nearest 0.001 cm, and in [1] range 3.0 to 5.0 mm. Evidence of repeat readings of D. [1] (ii) Absolute uncertainty in D in range 0.02 to 0.05 cm and correct method of [1] calculation to obtain percentage uncertainty. If repeated readings have been taken, then the absolute uncertainty can be half the range (but not zero if values are equal). (c) (i) l in range 19.0 to 21.0 cm, with unit, to nearest mm. [1] (iii) t in range 2.0 to 10.0 s and value(s) to nearest 0.1s or 0.01s. [1] (iv) Correct calculation of v. [1] (d) Justification for s.f. in v linked to s.f. in D and t. [1] (e) (ii) Second value of l. [1] Second value of t. [1] Second value of t > first value of t. [1] (f) (i) Two values of k calculated correctly. [1] (ii) Sensible comment relating to the calculated values of k, testing against a criterion [1] specified by the candidate. GCE AS/A LEVEL – May/June 2013 9702 34 (g) (i) Limitations 4 max. (ii) Improvements 4 max. Do not credit A two readings are not enough (to take more readings and plot a “repeat readings” on draw a conclusion) graph / take more readings and its own / few readings / calculate more k values and only one compare reading / take more readings and (calculate) average k

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