2021 H2 Prelim Phy P4_MS

Mark Scheme for Practical Qn Marking Point Marks 1(a)(i) Raw L to the nearest 0.1 cm and final value in the range 11.5–12.5 cm. 1 1(a)(ii) 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 1(b)(i) All raw times measured either to the nearest 0.1 s or all to the nearest 0.01 s. Evidence of measurement of nT repeated where nT ⩾ 10.0 s. Value of T in the range 0.5 s ⩽ T ⩽ 1.0 s. 1 1 1 1(b)(ii) Calculation of T2 correct. 1 1(b)(iii) Justification of the number of significant figures in terms of the number of s.f. in (raw) time only. 1 1(c)(i) Raw L to the nearest 0.1 cm and final value in the range 5.5–6.5 cm. 1 1(c)(ii) Second value of T < first value of T. 1 1(d)(i) Calculated correctly two values of k with unit and recorded to the least no. of sf among T and L. The final k values must not be fractions. Unit: cm0.5 s-1 or equivalent 1 1 1(d)(ii) Justification of Relationship Note: The given relation is valid for a compound pendulum.  Calculated correctly %kuncertainty = ∆ k kave x 100% OR %kuncertainty = ∆ k ksmaller x 100%  ∆ k=|k1 - k2 | OR ∆ k =|k1 - k2 |/2  Chose a criterion from the value in (a)(ii).  Concluded that results do not support the suggestion if %kuncertainty > the criterion chosen. OR Concluded results support the suggestion if %kuncertainty  the criterion chosen. (Expected) 1 1 1(e) Correct calculation of g using candidate’s second k and in range 9.0 m s-2 ⩽ g ⩽ 11.0 m s-2. 1 Fig. 1 Excel-Generated Theoretical Table for Q1 For internal use only DHS2021 1

Total 14 For internal use only DHS2021 2

Qn Marking Point Marks 2(a) R measured while resistor is in operation i.e., 1 Value of RA, RB and RC with unit in the range 64 - 72 Ω. 1 Fig. 2a Excel-Generated Theoretical Table for Q2a 2(b)(i) Value of I with unit in the range 30.0–50.0 mA. 1 2(c) Seven sets of readings of R: 22.7 Ω, 34.0 Ω, 45.3 Ω, 68.0 Ω, 102 Ω, 136 Ω & 204 Ω Six sets of readings of R 2 or 1 Column headings: Each column heading must contain a quantity, a unit, and a separating mark where appropriate. The presentation of quantity and unit must conform to accepted scientific convention, e.g. R / Ω, I / mA and . 1 Consistency of presentation: All raw values of I must be given to 0.1 mA or all to 0.01 mA. 1 Significant figures: All values of must be given to the same number of s.f. as the number of s.f. in raw I. Calculation: Values of are correct. 1 For internal use only DHS2021 3

Fig. 2b Excel-Generated Theoretical Table for Q2c 2(d) Stated appropriate graph to be plotted. 1 E is determined by the inverse of the gradient. X is determined by product of y-intercept and E. 1 Total 10 For internal use only DHS2021