A-LevelPhysicsDynamics9702/31 · Oct/Nov 2020 · Q220 Marks

In this experiment, you will investigate a cardboard shape falling down a wooden board.

(a)(i)You have been provided with a wooden board with nails attached. Set up the apparatus as shown in Fig. 2.1. [Figure 2.1] The angle between the wooden board and the bench is θ. Adjust the apparatus until θ is between 80° and 89°. Measure and record θ. θ =[1]
(a)(ii)Calculate sin θ. sin θ =[1]
(a)(iii)Justify the number of significant figures that you have given for your value of sin θ.[1]
(b)(i)Firmly press the adhesive putty centrally onto the cardboard shape as shown in Fig. 2.2. [Figure 2.2] Flatten the adhesive putty so that it has a thickness of approximately 5 mm. Hold the cardboard shape centrally above the wooden board with the adhesive putty touching the board, as shown in Fig. 2.3. [Figure 2.3] When the cardboard shape is released, it follows a path between the nails towards the bench. The time between releasing the shape and the shape touching the bench is t. Measure and record t. t = s[2]
(b)(ii)Estimate the percentage uncertainty in your value of t. Show your working. percentage uncertainty =[1]
(c)(i)Adjust the apparatus and determine the smallest angle at which the shape will still fall to the bottom of the wooden board after release. Measure and record θ. θ = Calculate sin θ. sin θ =[2]
(c)(ii)Measure and record t. t = s[2]
(d)(i)It is suggested that the relationship between θ and t is sin θ = k/t where k is a constant. Using your data, calculate two values of k. first value of k = second value of k =[1]
(d)(ii)Explain whether your results support the suggested relationship.[1]
(e)(i)Describe four sources of uncertainty or limitations of the procedure for this experiment. 1. 2. 3. 4.[4]
(e)(ii)Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures. 1. 2. 3. 4.[4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[1] 2(a)(i) Value(s) of raw θ to the nearest degree.
[1] 2(a)(ii) Correct calculation of sin θ.
[1] 2(a)(iii) Justification for significant figures in sin θ linked to s.f. in θ.
[1] 2(b)(i) Value of time t in range 0.5-3.0 s.
[1] 2(b)(i) Evidence of repeat values of t.
[1] 2(b)(ii) Percentage uncertainty based on an absolute uncertainty in t in range 0.2-0.5 s. If repeat readings have been taken, then the absolute uncertainty can be half the range (but not zero) if the working is clearly shown. Correct method of calculation to obtain percentage uncertainty.
[1] 2(c)(i) Second value of θ recorded.
[1] 2(c)(i) Second value of θ less than 70.0°.
[1] 2(c)(ii) Second value of t recorded.
[1] 2(c)(ii) Second value of t greater than first value of t.
[1] 2(d)(i) Two values of k calculated correctly. The final k values must not be fractions.
[1] 2(d)(ii) Valid comment consistent with the calculated values of k, testing against a criterion stated by the candidate.
[1] 2(e)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”).
[1] 2(e)(i) B Difficulty in measuring time t with a reason, e.g. time interval is short/percentage uncertainty is large/difficult to release shape and start stop-watch simultaneously/difficult to judge when to stop timing.
[1] 2(e)(i) C Difficulty linked to the practical set up of the board, e.g. holding with one clamp, board is not square to bench/board is not stable/board tilts to side.
[1] 2(e)(i) D Difficulty linked to release, e.g. force applied varies/starting position may vary/adhesive putty sticks (affects friction).
[1] 2(e)(i) E Difficulty with the angle with reason, e.g. setting or adjusting the angle when changing the clamp/difficult to make fine adjustments to the angle. 1 mark for each point up to a maximum of 4.
[1] 2(e)(ii) A Take more readings and plot a graph or take more readings and compare k values (not “repeat readings" on its own).
[1] 2(e)(ii) B Improved method to measure t, e.g. timer and pressure/contact switch at release point and/or at bottom or video with timer/frame-by-frame.
[1] 2(e)(ii) C Improved method to support board, e.g. use more than one clamp/clamp both sides/support with a block.
[1] 2(e)(ii) D Improved method of release, e.g. use of a stop/use of a card gate.
[1] 2(e)(ii) E Improved method to make fine adjustments to angle, e.g. scissor jack/use of screw thread on a clamp. 1 mark for each point up to a maximum of 4.