2020 ASRJC H1 Physics Prelims P1 Answers

1 8867/01/ASRJC/2020Prelim [Turn Over Anderson Serangoon Junior College 2020 H1 Physics Prelim Solution Paper 1 (30 marks) 1 2 3 4 5 6 7 8 9 10 D C A B A A C D C A 11 12 13 14 15 16 17 18 19 20 B D A A C C B C B B 21 22 23 24 25 26 27 28 29 30 D D C B B B D A D C 1 D mass of raindrop = ~ 0.05 g 2 C density of ruler = 13.78 /(31.2 × 0.32) = 1.3802 g cm−3 fractional uncertainty of density = 0.1 31.2 + 0.02 0.32 + 0.01 13.78 = 0.066 percentage uncertainty of density = 0.066 × 100% = 6.6 % actual uncertainty of density = 0.066 × 1.3802 = 0.09 g cm−3 Hence, density = 1.38 ± 0.09 g cm−3 3 A velocity of motorcyclist relative to passenger on car, vR = vM⃗⃗⃗⃗ − vC⃗⃗⃗⃗ = vM⃗⃗⃗⃗⃗⃗ + ( − vC⃗⃗⃗⃗ ) Hence, answer is A. 4 B Area under acceleration time graph represents the change in velocity of the object. Hence, the speed at point B will be greatest. 5 A Both stones have the same initial horizontal velocity and hence same final horizontal velocity. In the vertical component, both stones experience the same change in displacement (s). Using v2 = u2 + 2as, the same final vertical velocity will be obtained. 6 A After 1 sec, s = ut + ½ at2 = 0 + ½ (9.81)(1)2 = 4.905 m (equivalent to 2 storeys)

2 8867/01/ASRJC/2019PROMO After 2 sec, s = ut + ½ at2 = 0 + ½ (9.81)(2)2 = 19.62 (equivalent to 8 storeys) After falling 2s, the ball will be at the 2nd storey. 7 C Action-reaction must be of the same type. Weight is the gravitational force on the man due to the Earth. 8 D Since there is no external forces acting along the horizontal direction, COM applies. 9 C The impulse is the product of resultant force and time the force acts. 10 A Constant horizontal speed implies no net force in that direction, so the only force is the normal contact force acting upwards. 11 B Resultant force is zero in all cases. However, taking moments about the CG, assuming length of the square is d : A will result in a 2Fd – Fd = Fd clockwise moments C will result in 2Fd – Fd = Fd anticlockwise moments & D will result in 2Fd + Fd = 3Fd clockwise moments. 12 D Initial extension = 1/3.5 = 0.286 m Therefore, increase in EPE = ½ (3.5)[(0.286 + 0.40)2 – 0.2862] = 0.68 J. 13 A Let the mass of the ruler be m grams. Using principle of moments, taking moments about the pivot, m x 10 = 20 x 60 m = 120. When the 50 g mass is now hung on the string, let the pivot be at x cm mark, Using principle of moments, taking moments about the new pivot, 120 (50 – x) = 50 (100 – x) 600 – 12x = 500 – 5x 7x = 100 x = 14 cm

3 8867/01/ASRJC/2020Prelim [Turn Over 14 A Considering the effect of viscous force, the body would eventually reach terminal velocity. Hence: Since work has to be done ag