A-LevelPhysicsDynamics9702/33 · May/June 2020 · Q220 Marks

In this experiment, you will investigate the result of a collision between two cylinders.

(a)• The wooden cylinder labelled A has diameter D. Measure and record D. D = • The wooden cylinder labelled B has diameter d. Measure and record d. d =[2]
(b)(i)You have been provided with a wooden strip with a line drawn on one face. Use the stand, boss and clamp to set up the wooden strip in the position shown in Fig. 2.1. The end near the line should touch the bench and the other end should be approximately 5cm above the bench. [Figure 2.1] • Place cylinder B approximately 30cm from the end of the strip. [Figure 2.2] The distance between the end of the strip and B is L, as shown in Fig. 2.2. Measure and record L. L =[1]
(b)(ii)• Place cylinder A on the line on the strip as shown in Fig. 2.3. [Figure 2.3] • Release A. • A will roll down the strip and along the bench until it collides with B. B will roll and then come to rest as shown in Fig. 2.4. The distance between B and the end of the strip is l, as shown in Fig. 2.4. [Figure 2.4] Measure and record l. l =[2]
(b)(iii)Estimate the percentage uncertainty in your value of l. Show your working. percentage uncertainty =[1]
(b)(iv)Calculate (l – L)2. (l – L)2 =[1]
(c)• Measure and record the diameter D of cylinder C. D = • Using cylinder C instead of cylinder A on the wooden strip, repeat (b)(i), (b)(ii) and (b)(iv). L = l = (l – L)2 =[3]
(d)(i)It is suggested that the relationship between l, L, D and d is (l – L)2 = k(D – d)3 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 (May/June 2020). The mark or mark type is shown in brackets.

Value of D in the range 2.300–2.500 cm with unit and to the nearest 0.01 cm or 0.001 cm.
Value of d in the range 1.100–1.300 cm with unit and to the nearest 0.01 cm or 0.001 cm.
Value of L in the range 29–31 cm with unit and to the nearest 0.1 cm.
Final value of l in the range 40–80 cm with unit. Raw readings to the nearest mm.
Evidence of repeats.
Percentage uncertainty in l based on an absolute uncertainty of 2–5 mm.
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.
Correct calculation of (l– L)².
Second value of D.
Second values of L and l.
Quality: Second value of l < first value of l.
Two values of k calculated correctly.
Valid comment consistent with calculated values of k, testing against a criterion stated by the candidate.
A Two readings are not enough to draw a (valid) conclusion (not 'not enough for accurate results', 'few readings').
B Problem in placing cylinder A on the line (e.g. because cylinder covers line when placed).
C Narrow strip so A (or C) not centrally placed at release.
D A (or C) not hitting B 'full on'.
E Large step at bottom of strip causes deviation.
F Uneven friction of surface of bench.
G Difficult to measure L (or l) with a reason e.g. parallax/rule not touching edge of ramp.
1 mark for each point up to a maximum of 4.
A Take more readings and plot a graph or take more readings and compare k values (not 'repeat readings' on its own).
B Improved method of releasing A (or C) from the same height each time e.g. a stop.
C Use wider strip.
D Improved method of guiding A (or C) after rolling down strip e.g. place apparatus in a channel.
E Use a thinner strip/bevelled edge.
F Provide smoother/more even surface for A (or C) to roll horizontally.
G Improved method to measure L (or l) e.g. place apparatus on a grid of 1 mm graph paper/use set square.
1 mark for each point up to a maximum of 4.