2024 CCHY P2 PRELIM QP

2 2024 CCHY Preliminary Examination Physics (6091/02) / Sec 4 Express [Turn Over Section A Answer all the questions. 1 A hovercraft moves on a cushion of air which is trapped underneath it. The trapped air reduces friction. (a) The hovercraft starts from rest and, as it starts, the propeller produces a forward force F of 28 000 N. The mass of the hovercraft is 25 000 kg. Calculate the initial acceleration of the hovercraft. You may assume there is no friction. acceleration = .................................. [2] (b) Some time later, the hovercraft reaches a steady velocty, even though the force F is unchanged. Explain, in terms of forces acting on the hovercraft why the velocity is now constant. ....................................................................................................................................... ....................................................................................................................................... ................................................................................................................................... [2] [Total: 4]

3 2024 CCHY Preliminary Examination Physics (6091/02) / Sec 4 Express [Turn Over 2 There is no atmosphere on the Moon. An astronaut on the Moon drops a feather and a hammer from the same height at the same time. They both accelerate downwards at 1.6 m/s 2 and hit the ground at the same time. (a) The weight of the hammer is much larger than that of the feather. Explain why their accelerations are equal. ...................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .................................................................................................................................... [3] (b) The feather takes 1.5 s to fall to the ground from rest. (i) Calculate the velocity of the feather as it hits the ground. velocity = ......................................................... [2]

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