MI 2024 PU3 H2 PHYSICS PRELIM P2 ANS

2024 PU3 H2 Physics Prelim Paper 2 Suggested Answers 1 (a)(i) The vertical acceleration of the ball is constant in magnitude (9.81 ms-2) and directed downwards throughout the path. Hence as the ball moves from the ground to the highest point, vertical velocity decreases at a constant rate till vertical velocity reaches zero. As the ball moves from the highest point towards the ground, vertical velocity increases at constant rate. B1 B1 B1 (a)(ii) The horizontal acceleration of the ball is zero throughout the path. Hence the horizontal velocity is constant in magnitude. B1 B1 (b)(i) Considering the ball just after it leaves the ground to the point just before it hits the ground, 𝑣𝑦 = 𝑢𝑦 + 𝑎𝑦𝑡 15 sin 20𝑜 = ( −15 sin 20𝑜) + (9.81)𝑡 𝑡 = 30 sin 20𝑜 9.81 𝑠𝑥 = 𝑢𝑥𝑡 = (15 cos 20𝑜) 30 sin 20𝑜 9.81 = 14.7 m C1 C1 A1 (b)(ii) Considering the ball just as it drops down the cliff to just before it hits the ground. 𝑠𝑦 = 𝑢𝑦𝑡 + 1 2 𝑎𝑦𝑡2 70 = −15 sin 20𝑜𝑡 + 1 2 (9.81)𝑡2 t = - 3.29 (NA) s or 4.34 s 𝑠𝑥 = 𝑢𝑥𝑡 − 14.7 = (15 cos 20𝑜) (4.34) − 14.7 = 46.4 𝑚 C1 C1 C1 A1

2 (a) Gravitational field strength is defined as the force per unit mass acting on a small mass placed at a point in the gravitational field. A1 (b) For the same difference in gravitation potential, the distance between the potential lines is increasing as the distance from the surface of Mars, show that gravitation field strength is decreasing. A1 (c) Loss in gravitational potential energy = gain in kinetic energy of the satellite (90)(-6.0 –(-8.0)) x 106 = (1/2)(90)v2 v = 2000 ms-1 C1 A1 (d)(i) Centripetal force of the satellite is provided by the gravitation force. 𝑚𝑟(2𝜋 𝑇 )2 = 𝐺𝑀𝑚 𝑟2 𝑇 = √4𝜋2𝑟3 𝐺𝑀 = √ 4𝜋2(3.4 ×106+1.7 ×107)3 𝐺(6.4 ×1023) = 88607 s = 24.6 h C1 C1 (correct radius) A1 (d)(ii) KE = 1 2 𝑚𝑟2𝜔2 = 1 2 (90)(3.4 × 106 + 1.7 × 107)2 ( 2𝜋 88607) 2 = 9.42 x 107 J Alternative KE = 𝐺𝑀𝑚 2𝑟 = 𝐺(6.4 ×1023)(90) 2(3.4 ×106+1.7 ×107) = 9.42 x 107 J C1 A1 (d)(iii) Due to work done against friction, total energy of the satellite decreases, causing the satellite to fall towards Mars (or radius of orbit decreases). As the satellite fall towards Mars, it experiences a loss in gravitational potential energy and an increase in kinetic energy. (Or Since KE = GMm/2r as radius decreases, KE increases) B1 B1

3 (a) Despite both being at 100 C , steam transfers more (heat or thermal) energy to the skin than boiling water. This is because steam releases (heat) energy proportional to the latent heat of vaporisation during condensation in addition to the heat energy released on cooling of condensed water on skin. This is much h