A-LevelPhysicsOscillations9702/33 · Oct/Nov 2020 · Q220 Marks

In this experiment, you will investigate the oscillations of a square shape.

(a)(i)• Bend the wire to form a square shape so that the length L of each side is approximately 12cm, as shown in Fig. 2.1. [Figure 2.1] • Use the wire cutters to remove any excess wire. • Measure and record L. L = .............................................................. cm[1]
(a)(ii)Estimate the percentage uncertainty in your value of L. Show your working. percentage uncertainty = ..............................................................[1]
(b)(i)• Place the cork in the clamp and attach the clamp to the stand using the boss. • Hang the wire square from the pin as shown in Fig. 2.2. [Figure 2.2] • Gently displace the wire square and release it so that it oscillates as shown in Fig. 2.3. [Figure 2.3] • Determine the period T of the oscillations. T = .............................................................. s[3]
(b)(ii)Calculate T². T² = .............................................................. s²[1]
(b)(iii)Justify the number of significant figures you have given for your value of T².[1]
(c)• Remove the wire square from the pin. • Form a new square shape from the wire so that L is approximately 6 cm. • Use the wire cutters to remove the excess wire. • Measure and record L. L = .............................................................. cm • Repeat (b)(i) and (b)(ii). T = .............................................................. s T² = .............................................................. s²[2]
(d)(i)It is suggested that the relationship between T and L is T² = L/k 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)An approximate value for the acceleration of free fall g is given by g = 46.5 k. Use your second value of k to calculate a value for g. g = .............................................................. ms⁻²[1]
(f)(i)Describe four sources of uncertainty or limitations of the procedure for this experiment. 1. 2. 3. 4.[4]
(f)(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] Raw L to the nearest 0.1 cm and final value in the range 11.5–12.5 cm.
[1] Percentage uncertainty based on an absolute uncertainty ΔL in the range 2–5 mm. 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] All raw times measured either to the nearest 0.1 s or all to the nearest 0.01 s.
[1] Evidence of measurement of nT repeated where n ≥ 5.
[1] Value of T in the range 0.5 s < T≤ 1.0 s.
[1] Calculation of T² correct.
[1] Justification of the number of significant figures in terms of the number of s.f. in (raw) time only.
[1] Second values of L and T.
[1] Second value of T < first value of T.
[1] Two values of k calculated correctly. The final k values must not be fractions.
[1] Valid comment consistent with the calculated values of k, testing against a criterion stated by the candidate.
[1] Correct calculation of g using candidate's second k and in range 2.0 ms⁻² ≤ g < 20.0 ms⁻².
[4] A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”).
[4] B Difficulty in measuring time or T with a reason, e.g. judging when to start or stop the stop-watch, judging start/end/complete oscillation.
[4] C Difficulty in measuring L with a reason, e.g. wire is not straight/is kinked/has rounded corners.
[4] D Corners are not at right angles or square not complete/joined or shape changes when suspended/during oscillation.
[4] E Oscillations are not in one plane or square catches on drawing pin.
[4] A Take more readings and plot a graph or take more readings and compare k values (not “repeat readings" on its own).
[4] B Method of improving time or T, e.g. fiducial marker at centre/video (or record or film) and timer (or frame-by-frame)/place a grid behind the apparatus.
[4] C Method of improving L, e.g. use thicker/stiffer wire or use a former/shaping block.
[4] D Method of improving the setting of 90° corners, e.g. use a set square or protractor with appropriate reason or method of fixing ends, e.g. use adhesive putty/tape with appropriate reason.
[4] E Method of improving oscillation, e.g. longer pin/use of guide with detail/groove in pin/use a nail/use a hook.