Whitley Prelim Ans

2024 4E Physics Prelim Answers Paper 1 1 C 11 D 21 D 31 C 2 B 12 B 22 B 32 A 3 B 13 A 23 B 33 B 4 C 14 B 24 B 34 B 5 D 15 A 25 A 35 C 6 A 16 D 26 D 36 A 7 A 17 A 27 D 37 A 8 C 18 D 28 A 38 D 9 B 19 A 29 D 39 C 10 D 20 B 30 D 40 B Paper 2 1ai Fill the measuring cylinder with 50cm3 of water. Fully submerge the rock into the measuring cylinder. [1] The difference in reading is the volume of rock Q. [1] 1aii The volume is large and rock R may not be able to fit into the measuring cylinder. [1] 1b Rock S. the density of S is 5.6g/cm3 while P, Q and R is approximately 4.6 g/cm3. [1] 2ai Resultant force is zero. 2aii The object must move a distance. 2aiii Constant velocity 2b F = ma 100 – 85 = 25a a = 0.6 m/s2 2c The friction may not be constant. [1] Hence, the resultant force will change [1] and acceleration is not constant. 2d [1] – curve of decreasing gradient from 10 – 11.5s [1] – constant line from 11.5-12s 3a Density of the ladder is not uniform. 3b Moment = fd = 8 X 10 X 0.90 [1] = 72 Nm clockwise [1]

3c Taking moments about pivot, Sum of clockwise moments = sum of anticlockwise moments 8X10X0.90 + L X 0.54 = 87 X 1.3 L = 76.1 N (upwards) 4a KE = ½ mv2 = ½ (0.400)(2.5)2 = 1.25 J 4bi work done = area under the graph 1.25 = ½ x PQ x 14 PQ = 0.18 m 4bii smooth curve from v = 2.5 at x = 0 to v = 0 at Q curve with increasing gradient 5ai energy transmitted by electromagnetic waves / infra-red rays infra-red or visible < λ < microwaves (scores 2/2 if mentioned infrared in at least one) 5aii1 air is a poor conductor 5aii2 convection not the process as convection current occurs (primarily) upwards / hot air rises 5bi Pt = mlv 120 x 1 = 0.05 x lv lv = 2400 J/g (or 2.4 x 106 J/kg) 5bii work/energy is required to overcome the forces of attraction / to break the bonds of the water molecules kinetic energy / speed of the water molecules does not increase / is constant 6ai compressions and/or rarefactions are closer together OR more compressions and/or rarefactions 6aii layers closer together at compressions layers farther apart at rarefactions 6bi there is always a time difference / time difference is not zero 6bii v = d / t = 1200 / 3.6 = 333 m/s 7a distance between the optical centre and principal focus / focal point 7bi 1. straight line ray from A to B AND lens at intersection of ray and axis. Include label L. 2. ray from A parallel to principal axis, bent at lens to pass through B. F at intersection of ray and axis. Include label F. 3. any third ray from A to B AND bent at lens. 7bii 1. reduced / decreases 2. diminished / smaller 8a The cloth transfers its electrons to the plastic rod during the rubbing process. Hence the plastic rod becomes negatively charged.

8b When the metal rod is held above the plastic rod, the negative charges in the plastic rod will repe