A-LevelPhysicsOscillations9702/33 · May/June 2021 · Q220 Marks

In this experiment, you will investigate the oscillations of a loaded wooden strip.

(a)You have been provided with a rectangular wooden strip with a hole in its centre. • Use some of the adhesive putty to attach the two 100g masses as near as possible to one end of the strip, as shown in Fig. 2.1 and Fig. 2.2. • The distance between the centre of the masses and the hole is d, as shown in Fig. 2.1. Measure and record d. d =[1]
(b)Estimate the percentage uncertainty in your value of d. Show your working. percentage uncertainty =[1]
(c)(i)• Attach the two 50 g masses to the other end of the strip so that the distance between the centres of these masses and the hole is also equal to d. • Set up the apparatus as shown in Fig. 2.3. • The distance between the string loop and the nail in the centre of the strip is b. Adjust the position of the string loop and spring until b is approximately 10cm. • Adjust the heights of the bosses until the strip is horizontal and the spring and string loop are vertical. • Measure and record b. b =[1]
(c)(ii)Calculate α where α = b/d α =[1]
(c)(iii)Justify the number of significant figures that you have given for your value of α.[1]
(d)• Move the end of the strip with the 100g masses down through a short distance. • Release the end of the strip. The strip will oscillate up and down. • Take measurements to determine the period T of these oscillations. T =[2]
(e)• Change the value of b to approximately 20 cm. • Adjust the heights of the bosses until the strip is horizontal and the spring and string loop are vertical. • Measure and record b. b = • Repeat (c)(ii) and (d). α T =[2]
(f)(i)It is suggested that the relationship between T and α is T = C/α where C is a constant. Using your data, calculate two values of C. first value of C = second value of C =[1]
(f)(ii)Explain whether your results support the suggested relationship.[1]
(g)Theory suggests that C = 2π√(3m/k) where m is 0.100 kg and k is the spring constant of the spring. Use your second value of C to determine a value for k. Give an appropriate unit. k =[1]
(h)(i)Describe four sources of uncertainty or limitations of the procedure for this experiment.[4]
(h)(ii)Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures.[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 2021). The mark or mark type is shown in brackets.

2(a) Final value for d with unit and in the range 28.0–40.0 cm.
2(b) Percentage uncertainty based on absolute uncertainty in the range 2–6 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.
2(c)(i) Measurement of raw b to the nearest mm. Final value with unit and in the range 9.0-11.0 cm.
2(c)(ii) Correct calculation of α.
2(c)(iii) Justification for the number of significant figures in α linked to s.f. in b and d.
2(d) Final value for T with unit and in the range 1.50-2.50 s.
2(d) At least two measurements of nT where n ≥ 5.
2(e) Second values of b and T.
2(e) Second value of T < first value of T.
2(f)(i) Two values of C calculated correctly. The final values must not be written as fractions.
2(f)(ii) Valid comment consistent with calculated values of C, testing against a criterion stated by the candidate.
2(g) Value of k correctly calculated from the second value of C and with consistent unit, i.e. N m¯¹ or kg s-2.
2(h)(i) A Two readings are not enough to draw a (valid) conclusion (not "not enough for accurate results”, “few readings").
2(h)(i) B Masses falling off/masses stick to a small surface area/not enough adhesive putty for the masses/adhesive putty not strong enough to hold masses.
2(h)(i) C Difficult to judge when the wooden strip is horizontal/difficult to set wooden strip horizontal or difficult to judge or set the spring or string vertical.
2(h)(i) D Difficulty measuring d with a reason, e.g. finding/determining the centre of the mass/hole or difficulty measuring b with a reason, e.g. finding/determining the centre of the nail/holding the ruler parallel to the strip/set-up wobbly/holding ruler in mid-air.
2(h)(i) E Difficult to judge/determine/decide when an oscillation starts/finishes/is complete.
2(h)(i) F Different modes of oscillation/string moves during oscillation or strip bends/twists/flexes (during oscillation).
2(h)(ii) A Take more readings and plot a graph or take more readings and compare C values (not “repeat readings” on its own).
2(h)(ii) B Wider strip/named method for improving the adhesion of the masses, e.g. glue/tape with reference to masses.
2(h)(ii) C Method of ensuring strip is horizontal, e.g. use a spirit level or method to ensure spring/string is vertical, e.g. use a plumb-line.
2(h)(ii) D Improved method to measure b or d, e.g. add a scale to the strip/mark on the strip/clamp ruler.
2(h)(ii) E Fiducial marker at the centre of the oscillation or video/record/film with timer in view/play back frame by frame.
2(h)(ii) F Use a thicker/stiffer/laminated strip or sand to make rougher/add notch to wooden strip or rod/stick sandpaper to wooden strip or rod.