MI 23M1PrelimAS (H2 PHYSICS P2)

[Turn over 2023 Prelim Exams (Solutions) PU3 H2 Physics 9749 Paper 2 Qn Answers Marks 1 a Since the units of all the terms are the same, the equation is homogenous. units of v2, u2, and 2as presentation and conclusion B1 B1 b 𝑚𝑎𝑠𝑠 = (𝑙𝑒𝑛𝑔𝑡ℎ × 𝑤𝑖𝑑𝑡ℎ × ℎ𝑒𝑖𝑔ℎ𝑡) × 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 = (1.99 × 1.95 × 2.02) × 1.24 = 9.7199 = 9.71 𝑔 𝐵𝑦 𝑐𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑖𝑛𝑔 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 / 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑢𝑛𝑐𝑒𝑟𝑡𝑎𝑖𝑛𝑡𝑦: 𝛥𝑚 𝑚 = 𝛥𝑙 𝑙 + 𝛥𝑤 𝑤 + 𝛥ℎ ℎ + 𝛥𝜌 𝜌 = 0.01 + 0.01 + 0.01 + 0.05 1.24 = 0.070323𝛥𝑚 = 0.070323 × 9.7199[∗ 𝑀1] = 0.68353 = 0.7 𝑔 𝑚𝑎𝑠𝑠 = (9.7 ± 0.7) 𝑔 Alternatively, max-mean method: mmax = (1.99 x 1.01)(1.95 x 1.01)(2.02x1.01)(1.29) = 10.418 g 𝛥𝑚 = 𝑚𝑚𝑎𝑥 − 𝑚𝑚𝑒𝑎𝑛 = 10.418 − 9.7199 = 0.7 𝑔 C1 C1 C1 A1 (C1) (C1)

2 2 a Use of mgh = ½ m v2 and makes h subject h = 14.7 or 15 m A1 bi Calculate the final vertical velocity at C (using v = 0 + at=9.81x1.6) v = 15.7 or 16 m s-1 C1 A1 bii Straight line of positive gradient) Starting at 0 ms-1 and ends at 16 ms-1 at 1.6 s. A1 biii Use of pythagoras' theorem: resultant v2 = 15.72 + 172 v = 23 or 23.1 m s-1 M1 c slope: smaller change in vertical component of velocity/ smaller change in vertical component of momentum by Newton’s second law, the force experienced = rate of change of momentum is less, so less risk of injury M1 A1 3 ai Archimedes’ Principle states that the upthrust on a body completely or partially submerged in a fluid is equal in magnitude and opposite in direction to the weight of the fluid the body displaces. B1 aii Pressure increases with depth in a fluid. When an object is submerged in a fluid, bottom is at a greater depth than at the top, hence, the pressure is greater at the bottom than at the top of the object. The difference in pressure results in a net upward force acting on the object, which is upthrust. B1 B1 b C1 C1 A1 c A1

3 [Turn over 4 (a) 1 mark for correct direction of arrows 1 mark for similar length of arrows in vertical direction B1 B1 (b) Since frictional force provides for the centripetal force, A1 (c) (i) For a surface which is banked, the horizontal component of the normal reaction is an additional source of the centripetal force. Since Centripetal Force = , an increase in the centripetal force would allow the rider to turn the corner at a higher speed without slipping, provide the mass of cyclist and bicycle and radius of turn remain constant. B1 B1 (ii) Considering forces acting on the rider/bicycle in the horizontal direction: ---------------------- (1) For the equilibrium in the vertical direction: --------------------(2) Solving (1) & (2), 🡪max velocity during turning v = 15.7 m s-1 C1 C1 A1 reaction force weight normal contact force friction weight

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