2024 NASS Sc(Phy)P2 MS

1 NGEE ANN SECONDARY SCHOOL Sec 4 Express Science(Physics) 5086 Preliminary Examination 2024 Marking Scheme Paper 2 Section A – Structured Questions (55 marks) 2 (a) F – f = ma 12 000 – 3200 = 2400a 8 800 = 2400 a a = 3.67 m/s2 M1 A1 (b) The retarding force continues to increase due to air resistance until it balances the forward force. When the total retarding force is equal to the driving force, resultant force is zero and the bus moves at constant speed. B1 B1 Total 4 1 (a) Acceleration is greater during the time from the 10th second to the 14th second than the time from the 5th second to the 10th second. B1 (b) Acceleration = gradient = 10/4 = 2.50 m/s2 M1 A1 (c) B1 – negative uniform gradient (d) Distance = area under graph = (5x6) + [1/2(6+10)x5] = 70.0 m M1 A1 Total 6 speed / ms-1 time / s 6 10 20 0 5 10 14 18

2 3 (a) B1 – Correct labelled 50 cm mark B1 – Correct weight drawn acting vertically down at 50cm mark (b) By Principle of Moments, taking moments about the pivot, sum of clockwise moment = sum of anticlockwise moment W x 0.1 m = 5 x 0.2 Nm W = 10.0 N M1 A1 Total 4 4 (a) Conduction B1 (b) (i) B1 (ii) Water at the bottom gets heated and expands, decreases in density and rises to the top. Cooler surrounding water that has higher density sinks in to take its place. This sets ups a convection current to transfer heat throughout the liquid. B1 B1 5 N Weight

3 (c) Intermolecular forces Spacing/Distance between molecules Water strong Close together Water vapour weak Far apart B1 B1 Total 6 5 (a) The plastic stopper is a poor conductor of heat hence reduces heat loss by conduction. OR The stopper prevents warm air from escaping whereby preventing convection and evaporation from taking place. B1 (b) Vacuum between double glass wall prevents convection/conduction as convection/conduction requires a medium to take place. B1 (c) The wall of the glass is silvered so that infra-red radiation is reflected back to the liquid. OR Silver is a poor emitter of heat hence heat is radiation away slowly. B1 Total 3 6 (a) Amplitude = 0.400 m B1 (b) Distance = 1.2(3) = 3.60 m B1 (c) Wavelength = 3.6/3 = 1.20 m B1 Total 3 7 (a) B1 – 2 rays drawn correctly B1 – Image drawn upright correctly with label I (b) Upright and magnified or virtual B1 Total 3

4 8 (a) 3 correct forces drawn and labelled [B2] minus [1] for each force missing (b) S