2025 HCI C2 Prelim H2 Physics P1 Ans

2025 HWA CHONG INSTITUTION (COLLEGE SECTION) C2 © Hwa Chong Institution 1 2025 C2 H2 Physics Prelim Exams Paper 1 Suggested Solutions 1 C 6 D 11 C 16 A 21 A 26 D 2 B 7 D 12 A 17 B 22 C 27 B 3 D 8 C 13 B 18 B 23 A 28 C 4 B 9 D 14 B 19 D 24 D 29 A 5 C 10 D 15 C 20 B 25 B 30 D 1 C 3 3 344volume (12) 7200 cm33 r= = = 2 B Upwards direction is taken as negative. Sandbag when released will continue to move upwards but with acceleration downwards. Sandbag will move vertically upwards till it slows down to zero velocity and then it will accelerate downwards. 3 D Since trolley A is faster than B, and they have the same mass, the net momentum before collision is towards the right and non-zero. Hence Option A is true. Option B is true by Newton’s Third Law. Option C is true. If B is moving to the left then so must be A (as A cannot pass through B) and net momentum will be towards the left which is not possible if momentum is conserved. Option D is false. Whether a collision is elastic or not depends on whether kinetic energy is conserved and not on the duration of the collision. 4 B Taking moments about the left end of the ruler, 2 (0.250)(0.200) (0.500)(0.0500) 0.075k x g g g= + = ------ (1) Taking moments about the right end of the ruler, 1 (0.750)(0.200) (0.500)(0.0500) 0.175k x g g g= + = ------ (2) Dividing (1) by (2): 2 1 0.075 3 0.430.175 7 k k = = = Distractors (remove from suggested solution for students): A: 1/3 → forget to account for mass of ruler B: 3/7 → Correct C: 7/3 → flipped B D: 3/1 → flipped A 5 C By the Principle of Floatation (or by considering the net force on the cube), the upthrust on the cube is equal to the weight of the cube. 3 00weight of cube mg Vg L g= = = 6 D The shelf is light, so its weight can be neglected. The centre of gravity of the system is thus at the centre of the book.

2 © Hwa Chong Institution 2 When the system is in rotational equilibrium, the lines of action of the forces must meet at a point: The three forces must form a closed vector triangle, so that net force is zero. 7 D ( ) 2 2 d kxdUF kx dx dx= − = − = − The negative sign indicates that direction of force is towards the reference point O. 8 C ( ) ( ) : sin : cos (0.8 ) tan 1.25 51.3 cc o N mg N F ma m g  = → = = = = = Option A: shift cos (0.8) Option B: swap the angles in resolving Option D: shift sin (0.8) 9 D The rotation of the Earth results in the acceleration of free fall being smaller than the gravitational field strength at the Earth’s surface, except at the poles where they are equal. 10 D As the orbital radius r increases, GMmGPE r=− b