Cambridge A Level Physics 9702 — 2012 Oct/Nov Paper 3 · Variant 3

1 In this experiment, you will investigate how the motion of a thin card shape depends on where the shape is supported. (a) You are provided with a T-shaped card. The card has a mark on it and 14 holes. Label the holes on the card, 1 to 14, starting from the top end as shown in Fig. 1.1. 1 14 mark Fig. 1.1 (b) (i) Set up the apparatus, placing the pin through hole number 9, as shown in Fig. 1.2. For Examiner’s Use stand split bung in clamp card card pin pin h mark bench side view front view Fig. 1.2 (ii) Measure and record the distance h between the pin and the mark. h = ............................................ m [1] (c) Displace the card shape to the left. Release the shape and watch its movement. For The shape will move to the right and then to the left again, completing a swing as shown Examiner’s in Fig. 1.3. Use one complete swing Fig. 1.3 Measure and record the time for at least 10 swings. Record enough readings to determine an accurate value for the time T taken for one complete swing. T = ................................................. [2] (d) Vary h, by changing the hole through which the pin is placed, and repeat (b)(ii) and (c) For until you have six sets of values of h and T. Examiner’s Use Include values of T 2h and h2 in your table. [9] (e) (i) Plot a graph of T 2h on the y-axis against h2 on the x-axis. [3] (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 (f) The quantities T and h are related by the equation For Examiner’s T 2h = P h2 + Q Use where P and Q are constants. Using your answers from (e)(iii), determine the values of P and Q. Give appropriate units. P = ...................................................... Q = ...................................................... [2] You may not need to use all of the materials provided. For Examiner’s

Mark scheme: 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. 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]

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2 In this experiment, you will investigate how the stopping distance of a model vehicle depends Use on its mass. (a) (i) Record the mass m of the model. This information is given on the card. m = ................................................... g (ii) Measure and record the total length L of the model, as shown in Fig. 2.1. L Fig. 2.1 L = ................................................. [1] (b) (i) Support the board as shown in Fig. 2.2. model block A board B C line bench s Fig. 2.2 Place the back wheels of the model on the line. This is position A. Release the model. It travels a distance of 40 cm down the board until all the wheels are on the bench. This is position B. The model moves a distance along the bench before stopping. This is position C. Distance s is measured from the end of the board to the front of the model as shown in Fig. 2.2. (ii) Repeat (b)(i) until s is approximately 60 cm. For It may be necessary to adjust the slope of the board before releasing the model. Examiner’s Use Do not adjust the slope of the board throughout the remainder of the experiment. Measure and record the distance s. s = ................................................. [2] (iii) Estimate the percentage uncertainty in your value of s. percentage uncertainty = ................................................. [1] (iv) Use your values from (a)(ii) and (b)(ii) to determine the distance x moved by the model between B and C, where x = s – L. x = ................................................. [1] (c) Replace the model at A. Release the model. Measure and record the time t taken to move from B to C and the distance s. Calculate x. t = ...................................................... s = ...................................................... x = ...................................................... [1] (d) (i) Calculate the average speed v of the model between B and C using the relationship x v = . t v = ................................................. [1] (ii) Justify the number of significant figures that you have given for your value of v. For Examiner’s .................................................................................................................................. Use .................................................................................................................................. ............................................................................................................................. [1] (e) (i) Fix the 100 g mass on top of the model using the Blu-Tack. (ii) Calculate and record the total mass M of the model and the 100 g mass. M = ................................................... g (iii) Repeat (c) and (d)(i). t = ...................................................... s = ...................................................... x = ...................................................... v = ...................................................... [3] (f) It is suggested that v remains constant when M is changed. Explain whether your results support the suggested relationship. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ..................................................................................................................................... [1]

Mark scheme: 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] 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]

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