TJC 2023 H2 Prelim Paper 4 Solutions

1 Name: _____________________________________ CG: ___________ Date: _____________ Question 1 Suggested Mark Scheme No Marking Instructions Mark Score (a)(i) d recorded to nearest 0.1 mm with unit (2 dp in cm) 1 (a)(ii) h recorded to nearest 0.1 mm or 1 mm with unit (1dp or 2dp in cm) D recorded to nearest 0.1 mm with unit (2 dp in cm) with evidence of repeat measurement 1 (b)(iii) x calculated correctly to correct s.f. (with substitution) 1 (b)(iv) Correct justification of s.f. in x linked to s.f. in D, d and h (lowest s.f.) 1 (c)(ii) Value of t to correct d.p. with unit (5.0 s ≤ t ≤ 9.0 s) Evidence of repeat timing 1 (c)(iii) Correct calculation of % uncertainty (1 or 2 sf) using sensible value of t (0.2 s ≤ t ≤ 0.5 s). 1 (d) Second value of x calculated correctly Second value of average t with correct dp and unit 1 1 (e)(i) Correct calculations of the two k values with correct unit 1 (e)(ii) Draw conclusion based on stated criterion. (e.g. not obeyed because % difference of k values > 2 times % uncertainty of t in (c)(iii)) 1 (f)(i) Sources of error might include: 1. Difficult to release small container from same position every time as placing fingers in water changes level of water surface making it difficult to maintain the same start point, affecting t 2. As the centre of gravity of the small container and marbles is located at one side of the container it does not always fall vertically and may hit the sides of the cylinder during descent, affecting t 3. Timing is too short making human reaction time a significant uncertainty in timing t 4. Difficult to identify end point as it is difficult to see the small container due to refraction/similar refractive indices of water, cylinder and container/glass curvature, affecting t 5. Bubble / air in container introduces extra buoyancy, affecting t 1 (f)(ii) One improvement each. Relevant points might include: 1. Better method to hold and release cylinder (e.g. use a pincer / make a mark for reference to ensure same water level for each release) 2. Method to attach string symmetrically / ensure symmetrical distribution of masses e.g. use glass beads/sand/modelling clay for even mass distributions 3. Use a longer tube / video the descent and view frame by frame 4. Method to identify end point (e.g. mark at bottom of cylinder/use colour container) 5. Puncture a small hole in the lid to release bubble / air 1 Total 12 Question 2 Suggested Mark Scheme No Marking Instructions Mark Score (a)(ii) x recorded to nearest mm with unit (or 1 dp in cm, 3 dp in m) 1 (b)(ii) V1 and V2.recorded to correct d.p. with unit (3 d.p. in V) with V2 < V1 1 (c) Collected and tabulated 5 sets of data (for x till 90.0 cm) V2 /V1 calculated correctly to correct s.f. 1 1 (d)(i) Linear graph with y-intercept. Appropriate scales – awkward scales (e.g. 3:10) are not allowed and scales must be chosen so that the plotted points occupy