MI 2024 PU3 H2 PHYSICS PRELIM P4 ANS

Mark Scheme and Suggested Solutions This document consists of XX printed pages and X blank page. [Turn over 2024 Preliminary Exams Pre-University 3 H2 PHYSICS 9749 / 04 Paper 4 Practical 26 August Candidates answer on the Question Paper. 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your name, class and admission number in the spaces provided at the top of this page. Write in dark blue or black pen on both sides of the papers. You may use an HB pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. Answer all questions. Write your answers in the spaces provided in this question paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. Give details of the practical shift and laboratory where appropriate in the boxes provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 16 2 8 3 19 4 12 TOTAL / 55 H

2 1 This investigation considers the size of the hole needed in a salt shaker for the salt to flow at a suitable rate. (a) You have been provided with a beaker labelled P containing 100 g of salt as shown in Fig. 1.1. Fig. 1.1 (i) Measure and record the depth x of salt in beaker P using the vernier calipers. Zero error = 0.00 cm x1 = 2.18 cm , x2 = 2.20 cm x = 2.18+2.20 2 = 2.19 cm x = …………………………………. [1] (ii) State a significant source of error in your value of x. [1] (iii) Estimate the percentage uncertainty in your value of x. ∆x = (0.01 + 0.04 )cm ∆𝑥 𝑥 × 100% = 0.05 2.19 × 100% percentage uncertainty = 2.3 % percentage uncertainty = …………………………………. [1] (b) You have been provided with two cards. Each card has a hole of a different size. (i) Measure and record the diameter d of the smaller hole. d1 = 0.46 cm , d2 = 0.47 cm d = 0.46+0.47 2 = 0.47cm d = …………………………………. [1] (ii) Determine the area A of the smaller hole. A = π(0.47 2 )2 𝐴 = 0.173 𝑐𝑚2 = 0.17 cm2 A = …………………………………. [1] x beaker salt 2.19 cm (2 d.p.) It was difficult to level the salt evenly within the beaker OR It was difficult to ensure that the tail of the vernier calipers was perpendicular to the based of the beaker 2.3 % (2 s.f.) 0.47 cm (2 d.p.) 0.17 cm2 (2 s.f.) [1] zero error recorded and considered in calculation. correct d.p. of x; Repeated readings recorded; and correct unit of x [1] A reasonable source of error stated Absolute uncertainty in the range of 2mm to 5mm (1.s.f.). [-1] either percentage uncertainty more than 2 s.f. [-1] either absolute uncertainty not 1 s.f. [-1] either (∆x and x) differs in d.p. [1] correct d.p. of d; Repeated readings recorded; and correct unit of d [1] A calculated correctly, correct s.f. of A (following from raw data); and correct unit of A. If Area stated as 1 s.f. no marks given.

3 [Turn over (c) (i) Fill the boiling-tube, as shown in Fig. 1.2, with salt from beaker P. Fig. 1.2 (ii) Cover the open end of the boiling-tube with the card that has the smaller hole. Use tape to attach the card to the boiling-tube. The hole should not be covered by tape. When the boiling -tube is inverted, it should not be possible for salt to leave the boiling-tube other than through the hole. (iii) Cover the hole with your finger. Invert the boiling-tube over the empty beaker Q. Remove your finger and allow the salt to flow through the hole into beaker Q for 50 seconds. It may be necessary to shake the boiling-tube gently to achieve constant flow. (iv) Tap beaker Q gently on the bench to ensure that the surface of the salt is level. Measure and record the depth y of salt in beaker Q. y1 = 1.24 cm , y2 = 1.29 cm y = 1.24+1.29 2 = 1.27 cm y = ……………………………………… (v) Estimate the mass m of salt in beaker Q. Assuming that the cross-sectional area of both beakers are the same, mass in Q mass in P = 𝑦 𝑥 m = 1.27 2.19 × 100 m = 57.99 g = 58.0 g m = …………………………………. [1] boiling-tube salt 1.27 cm (2 d.p.) 58.0 g (3 s.f.) Correct d.p. of y; Repeated readings recorded; and correct unit of y [1] m calculated correctly, correct s.f. of m (following from raw data); and correct unit of m.

4 (d) The recommended daily intake of salt for an adult is 5 g. Use your data to calculate the time that a shaker, with a hole the same size as that in (c)(ii) should be inverted to apply 5 g of salt to food. Assuming constant flow rate, 58.0 g time needed for 58.0 g to flow = 5 g time needed for 5 g to flow time needed for 5 g to flow = 5 × 50 58.0 time needed for 5 g to flow = 4.3 𝑠 time = …………………………………. [1] (e) It is suggested that the rate of flow R of salt is proportional to the area A of the hole. Use the card with the larger hole to take further measurements in order to investigate this suggestion. State and explain whether or not you agree with this suggestion. Present your measurements and calculated results clearly. For the smaller hole 𝑅1 = 58.0 50 = 1.16 g s−1 For the bigger hole, d = 0.60 cm 22 2d 0.60A = π = π = 0.28 cm44            When t = 10 s, depth z1 = 0.92 cm , z2 = 0.98 cm z = 0.92+0.98 2 = 0.95 cm 𝑚𝑄 100 = 0.95 2.19 𝑚𝑄= 43 g 𝑅2 = 43 10 = 4.30 g s−1 If R = k A, then the two experiment must yield the same k 𝑘1 = 𝑅1 𝐴1 = 1.16 0.17 = 6.82 g s−1m−2 𝑘2 = 𝑅2 𝐴2 = 4.30 0.28 = 15.4 g s−1m−2 % k difference = 𝑘2−𝑘1 1 2(𝑘1+𝑘2) ×100% = 8.58 11.1 ×100% = 77.3% Since % k difference of 77.3% is more than the uncertainty of x (2.3%), the rate of flow of salt is NOT proportional to the area of the hole. [6] 4.3 s (2 s.f.) [1] time calculated correctly, correct s.f. of time (following from raw data); and correct unit of time. [1] depth of salt, correct d.p. (1 d.p. for mm and 2 d.p. for cm); Repeated readings recorded; and correct unit [1] Correct calculation of A, correct s.f. of A with correct unit [1] mass collected calculated correctly, correct s.f. and correct unit [1] Rate of flow 𝑅 for both cards calculated correctly, correct s.f. of 𝑅 (following from raw data); and correct unit of 𝑅. 𝑅2 should be larger than. 𝑅1. Analysis [1] Both values of 𝑘 calculated correctly, correct s.f. of 𝑘 (following from raw data); and correct unit of 𝑘 [1] compare % difference with percentage uncertainty of x in (a)(iii); conclude correctly OR Draw conclusion based on stated criterion e.g. not obeyed because more than 20% difference in values of k.

5 [Turn over (f) A statement found on the internet says that: "The salt shaker may be distinguished primarily by the size of the holes, and then by the number of holes. Salt is coarser than pepper, and needs the larger hole. It is also heavier and flows much more freely than pepper, accordingly there are often fewer holes on the salt shaker to help control the flow. However, there is no manufacturing standard." Suggest changes that could be made to the salt investigation to study the flow of pepper from a shaker. Use smaller holes, pepper is finer Use more holes, does not flow as freely as salt Use a mass balance to weigh the exact mass of pepper that flows out as pepper can stick to the side of beaker and height of pepper will be inaccurate. Pour the pepper carefully with the boiling tube lowered into the beaker/ Use a taller beaker /Use a cover to prevent pepper that f