2023 9749 H2 Physics MS EJC Suggested Solutions

©EJC 2024 9749/H2 PHYSICS 2023 PHYSICS SUGGESTED MARK SCHEME Maximum Mark: 190 9749 October/November 2023 Paper 1 Multiple Choice Question Key Question Key Question Key 1 C 6 B 11 B 2 D 7 C 12 C 3 A 8 B 13 B 4 C 9 C 14 D 5 B 10 A 15 B 16 D 21 B 26 C 17 A 22 D 27 D 18 A 23 C 28 A 19 D 24 A 29 A 20 B 25 D 30 C 1 The error varies each time a measurement is take. 2 From graph: 21 2 1 2 = + −= + s ut at qppr r 2  r ( ) ( ) 1 2 1 2 = +− = + pr q p r q pr 3 Notice that all options has Ft , which is momentum. So let’s focus on momentum. 2= ∆= = ⇒∝ Ft p p mE Ft E Note: The change in momentum is identical to the initial momentum since the final momentum is zero. 4 Notice the u and v are speeds, which is the magnitude of velocity. Apply understanding of relative speed of approach equal to relative speed of separation, taking care of the direction of the bodies.

2 ©EJC 2024 9749/H2 PHYSICS 2023 5 Split the metal into top half (mass m) and bottom half (mass ½ m). Let x be the distance between the c.g. and the centre of top half. m 1 2=xm (4 ) 4 cm3 − = x x Distance of c.g. from P, which is 6 cm from P: 46 4.7 cm3= −=d 6 Read question carefully to deduce that 60% of the loss in KE of wind is converted to electrical output of turbine. ( ) ( ) ( ) ( ) 22 22 22 drop in Power 60% 1 1260% 60% 2 10.6 9.7 4.0 1.52 40 W = −   = = −     = −  KE t mu v mVI u vtt 7 One year, one orbit. Half year, half orbit. 2 360 180 π π = ° = ° 8 Based on definition. 9 Interpretation of the diagram is key. A: spacecraft is falling towards Earth (possible as with any normal object) B: path is around Earth (possible with some initial velocity, then spacecraft moves in a circular path dues to centripetal force) C: Not possible D : path is away from Earth (possible if it had an initial velocity, it would just be slowing down as it moves) 10 The average force by N molecules on the wall is dues to the collision of N molecules on the wall. By Newton’s 3 rd Law, force by molecule on wall equals force by wall on molecules. 22 2 ∆∆= = = =∆∆   ave mv v v vF N Nm Nm Nm ptt p v Note: Δv = 2v due to change in direction. Δt is taken to be the time between consecutive collision with the same wall, 2∆= pt v 11 Notice that the gas is heated to double its thermodynamic temperature in Kelvin. 33 22 '2 '2 = = ∴= ⇒= U pV nRT TT UU 12 Notice thermal energy is applied, and both P and Q have the same mass. Since P’s temperature increases faster (larger gradient) than Q’s, hence P has a smaller heat capacity. Since P takes a longer time to melt fully (from the point it started to melt), it has a larger specific latent heat of fusion than Q. 13 Note that molar mass i