CCHM 2026 Physics P3 MS

1 2026 6091 Physics Prelim Paper 3 Answers Cap of 1 mark per instrument read to the wrong precision for the whole paper (reading off the graph is considered as 1 instrument). Cap of 1 mark for s.f. errors for each question. Cap of 1 mark for d.p. errors for each question. Cap of 1 mark for same type of units for each question. All working must be shown. No marks will be awarded for calculation question with no working. Calculations handling raw data => need to follow d.p./s.f. rule Calculations handling processed data => can give to 2 or 3 s.f. Copying error: Student drops zeros for a quantity. For eg: 1(c) V = 3.0 cm3, then 1(d) writes 3 cm3 in the working → Penalise 1 mark for copying error ecf for sf/dp: Give ecf and mark the sf/dp based on what student has written in working if there is no copying error. For eg: 1(c) V = 3 cm3 then 1(d) B = ρ V g = 1 x 3 x 0.010 = 0.03 N (1 s.f) is the correct answer Penalise if students write 1(d) B = ρ V g = 1 x 3 x 0.010 = 0.030 N (2 s.f) Two mistakes (eg: sf error and unit error made in part a) → Penalise 1 mark. If mistake is repeated (eg: the same unit error in part b) → Penalise another 1 mark 1(a)(i) MMO M is measured to 2 d.p and with correct unit M = 27.48 g B1 1(a)(ii) MMO m is measured to 2 d.p with correct unit and range of 49.00 g – 51.00 g m = 50.53 g Note: 1a(i) and 1a(ii) penalized once only for 2 d.p and unit. B1 1(b) MMO V is measured to 1 d.p and V ≤ 5.0 cm3 V = 3.0 cm3 AWW: Do not penalize if working is missing. B1 1(c) PDO B = ρ V g = 1 x 3.0 x 0.010 = 0.030 N Correct calculation and correct unit and calculated to 2 s.f B1

2 1(d) MMO p and q are measured to 1 d.p and must be less than 50.0 cm and p < q. p = 11.0 cm q = 25.0 cm Accept answers in metre. B1 1(e)(i) PDO 𝐵 = 𝑀𝑔 − 𝑚𝑔(𝑥 𝐿) = (27.48)(0.010) – (50.53)(0.010)(11.0 / 25.0) = 0.2748 (4 s.f) - 0.222 (3 s.f) = 0.053 N (3 dp) Correct calculation and correct unit and calculated to correct dp B1 1(e)(ii) ACE Appropriate calculation with values of B from (c) and (e)(i) % difference = (B1 - B2 ) / B1 x 100 = (0.030 – 0.053) / 0.030 x 100 = -76.7 % Appropriate conclusion with explanation. The experiment does not agree with the suggestion as the two values are not within the limits of experimental error as the percentage difference is more than 10 % (or 5 %). *Accept: % difference = (B2 - B1 ) / B2 x 100 M1 A1

3 1(f) ACE Correct source of error identified that can be improved Correct improvement that will reduce the error identified Any one Sources of error Improvement 1 The weight of the metre rule is not uniformly distributed. Ensure the metre rule is balanced when pivoted at the 50 cm mark before doing the experiment and put blu-tack on the metre rule to balance it if necessary. Reject: Replace the metre rule with a uniform metre rule. 2 The metre rule may not be exactly balanced (when p and q are recorded) Accept: The metre rule is not horizontal (when p and q are recorded) Measure the height of the metre rule above the table on its right and left side to ensure they are the same height. Reject: Repeat the experiment and take the average. 3 Only one set of p and q readings were measured but there could be other possible combinations which may cause differing B values to be calculated. Obtain 2 more sets of p and q values and use them to calculate the average value for the buoyancy force B. Reject: answers related to the surrounding environment (e.g: wind) Reject (because it is an apparatus error not an experimental procedure error): The string is thick and prevents the marking from being read accurately. Use thinner strings. Reject (because it is not for part d): Volume of string (submerged in the water) may cause the measured volume to be greater / inaccurate. Use thinner strings. M1 A1

4 2a(i) MMO - L is measured to 3 d.p - L is in the range of 0.495 m– 0.505 m - measured in metre L = 0.500 m B1 2a(ii) MMO - x is measured to 3 d.p - x is in the range of 0.105 m – 0.115 m - measured in metre Note: 2a(i) and 2a(ii) penalized once only for 3 d.p and metre. x = 0.110 m B1 2a(iii) PDO Average time for 10 oscillations = ( 10.4+10.3 2 ) = 10.4 s T = 10.4 10 = 1.04 s First mark: - Evidence of repeating the experiment (at least 2 readings) - Recording of time taken to 1 d.p. Second mark: - Evidence of taking at least 10 oscillations - Correct calculation of period T - T is in the range of 0.936 s – 1.14 s - T is calculated to correct sf (e.g: 3 sf) - Correct unit B1 B1

5 2(b) ACE Mark allocation No Item Marks 1 • Description of how the experiment is performed by changing the independent variable and measuring the dependant variable. • At least two timings of minimum 10 oscillations are recorded. • Calculation of √𝐿 or √𝑥. (B.O.D if seen in table) • Calculating of T and T2 (B.O.D if seen in table) 1 2 Repeating of steps to get at least 5 more values of the independent variable. • For independent variable L, L must be less than 150 cm. 1 3 Stating the control variable • Reject: angle of displacement (stated in question already) 1 4 Correct table with headers • Mark for L / m, √𝐿/√𝑚 , T / s and T2 / s2 1 5 Correct graph • Do not need to mark for the units • Do not penalize if statement for graph is not written 1 6 Determination of how to find g using either gradient or y-intercept with a simple description 1 B6

6 Example 1 independent variable: L, dependant variable: T, constant variable: x No Steps Marks 1. Set up apparatus as in Fig. 2.1. Do step (ai) for L=50 cm. Calculate √𝐿. B1 2 Do step (aii) for x=11 cm. 3 Do step (aiii). Record the time taken for 20 oscillations, t1. Repeat for another 20 oscillations, t2. Calculate the average time for 20 oscillations. Calculate the period T. Calculate T2. 4 Repeat steps 1 to 3 for L= 45 cm, 40 cm, 35 cm, 30 cm, 25 cm. B1 5 Keep x constant (at 11.0 cm by adjusting the bottom clamp). B1 6 Record all values in the table below: L/m √𝑳/√𝒎 t1 / s t2 / s tave / s T/s T2 / s2 - Mark for L / m, √𝐿/√𝑚 , T / s and T2 / s2 B1 7 Plot a graph of T2 against √𝐿. Graph: - Award mark only for a graph with line that does not pass through origin. - Do not need to mark for the units - Do not penalize if statement for graph is not written B1 8 (Choose two points on the line: (x₁, y₁) and (x₂, y₂).) Calculate gradient = (y2 – y1) / (x2 – x1) Calculate g = π2 gradient OR The y-intercept is the point where the line cuts the y-axis. Calculate g = 𝜋2√𝑥 𝑦−𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 or g = 𝜋2√11 𝑦−𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 1 T2 / s2 √𝐿/√𝑚

7 Example 2 independent variable: x, dependant variable: T, constant variable: L No Steps Marks 1. Set up apparatus as in Fig. 2.1. Do step (ai) for L=50 cm. B1 2 Do step (aii) for x=11 cm. Calculate √𝑥. 3 Do step (aiii). Record the time taken for 20 oscillations, t1. Repeat for another 20 oscillations, t2. Calculate the average time for 20 oscillations. Calculate the period T. Calculate T2. 4 Repeat steps 1 to 3 for x= 15 cm, 20 cm, 25 cm, 30 cm, 35 cm (by adjusting only the bottom clamp.) B1 5 Keep L constant (at 50.0 cm.) B1 6 Record all values in the table below: x/m √𝒙/√𝒎 t1 / s t2 / s tave / s T/s T2 / s2 - Mark for x / m, √𝑥/√𝑚 , T / s and T2 / s2 B1 7 Plot a graph of T2 against √𝑥. Graph: - Award mark only for a graph with line that does not pass through origin. - Do not need to mark for the units - Do not penalize if statement for graph is not written