2023 VS Phy S4_Prelim P1&2 Ans

Page 1 of 9 VS 2023 Preliminary Examination 2023 Prelim exam mark scheme Paper1 1 2 3 4 5 6 7 8 9 10 A C D D B B C B B C 11 12 13 14 15 16 17 18 19 20 C A D C B A C B B A 21 22 23 24 25 26 27 28 29 30 B B C B D A B B C A 31 32 33 34 35 36 37 38 39 40 D C A B A A C B D A Paper 2 Section A Qn Suggested solution 1a) displacement = ½ (5.0 x 30) – (1/2 x 3.0 x 30) = 75 – 45 = 30 m (b) acceleration of the cyclist = 30 / (2.0) = 15 m / s2 (c) The cyclist moves with constant deceleration from 2 s to 5 s. It moves with constant acceleration from 5 s to 8 s in the opposite direction. Or the cyclist moves with constant negative acceleration from 2 s to 8 s. It moves with constant velocity of 30 m / s in the opposite direction.

Page 2 of 9 3 (a) Efficiency is the percentage of total input energy that is converted to useful output energy. (b) Total input energy = 1.3 × 106 × 20s = 2.6 × 107 J Maximum height = 0.40 ×2.6 × 107 1500 ×10 = 693 m (d) Correct shape – 1 mark 2(a) Any 1 condition The resultant moment about any point is zero. or The resultant force acting on the door is zero. (b) Moment = 0.80 m x 35 N = 28 Nm (c) Taking moment about the hinge, Sum of Clockwise moment = Sum of anticlockwise moment 0.80 × 35 = F × 0.26 F = 108 N (3 s.f.) (d) Force F will remain larger than force P since its perpendicular distance from the hinge is smaller than P’s. The door is in equilibrium when it opens at a steady rate.

Page 3 of 9 (c) At point X, the gravitational potential energy of the roller coaster car is the maximum. As it moves to the lowest point between point X and Y, its kinetic energy is the maximum as its gravitational potential energy is converted to kinetic energy. At point Y, it possesses both kinetic energy and gravitational potential energy which is gained from the increase in its vertical height. (d) Work done is the product of the force exerted by the machine and the distance travelled in the direction of the force. 4 (a) Pressure is force per unit area. (b) Manometer (c) Pressure of the gas in the flask = atmospheric pressure - hpg = 1.0 × 105 – 0.32 × 13600 × 10 = 56480 = 56.5 kPa (d) The level of mercury at P will rise and level at Q will drop and their difference will be less than 320 mm. 5(a) 3.0 x 106 complete cycles are produced in a second. (b) The air particles vibrate/oscillate about their equilibrium position parallel to the direction of the wave motion. They transfer energy through a series of compression and rarefactions from one point to another. (c) distance = speed x (time