NYGH-2016-S3EOY-Physics P1 and P2 Ans

STUDENTS’ COPY 1 2016 Sec 3 End of Year PHYSICS Paper ANSWERS Paper 1 1….…5 6…...10 11....15 16….20 21….25 26.....30 CBBBA CABCB AABAA BCCBA DDDBD DCBAA 10 [B] Inertia is dependent on the mass and not on the pull of gravity. The mass of a body is the same on earth as on the moon. So, the inertia on the same body is the same on earth as on the moon. 11 [A] When the cable breaks, the lift and the man will both be falling freely. Net force on the man, FR = 800 N Since FR = W – R with R as the normal contact force and W as the weight. R = W – F R = 800 N – 800 N = 0N 12 [A] Let frictional force be f Net force = P – f = ma When multiplied by 3 on both sides, 3(P – f) = 3ma 3P – 3f = 3ma ….. (1) When force is increased to 3P, Net force = 3P – f = ma x …….(2) Comparing (2) with (1), ax must be more than 3a 21 [D] The pressure from liquid P and liquid are equal at the liquid levels that are exposed to atmospheric pressure. Hence 2l dP g = 1 l dQ g Therefore, density of Q, dQ is 2 times density of P, dP. Note: The liquid pressure at the base on the left is NOT equal to the liquid pressure at the base on the right because they are filled with different liquids. 27 [C] The man runs forward with velocity 2.5 ms-1. His image is moving towards him with velocity -2.5 ms-1. So, he will see himself running towards his image with a velocity 5.0 ms-1. 28 [B] In an optical fibre, a light ray changed direction due to total internal reflection and not refraction. Paper 2 1a) A pair of vernier calipers or vernier caliper (accept caliper or calipers) 1b) Student should have recorded the average length to 3 significant figures instead of 4. 1ci) g = W/m = 0.236/ 0.0239 = 9.87 ms -2 1cii) density = m/v = 23.9/ (2.24 × 1.91 × 2.05) = 2.72 g cm -3 or 2720 kg m-3 2a) using t = (v – u)/a = (0-16.0)/10 = 1.6 s 2b) using v = u + at = 16 + (-10)(4.0) = -24 m s -1

STUDENTS’ COPY 2 2c) 3a) The principle of conservation of energy st ates that energy cannot be created or destroyed but only changes from one form to another. 3b) Loss in height = (1.44 2 – 1.202)1/2 = 0.796 m Loss in GPE = (0.450)(10)(0.796) = 3.58 J 3c) Gain in KE = Loss in GPE ½ mv 2 = mgh; v = (2gh) 1/2 = 3.99 ms-1 3d) The law still applies, the carpet is rough and energy was dissipated as heat as the ball rolled across the carpet. (or work was done against friction) 4a) This lowers the centre of gravity of the toy to below the support Y, so that the toy is in a state of stable equilibrium. 4b) The weight of the toy creates an anticlockwise moment about the pivot. Therefore, the toy rotates anticlockwise and eventually returns to its original position. 5a) The angle of incidence is equal to the angle of reflection. The incident ray, the reflected ray and the norma