Jurong Prelim P2 Ans

1 JSS 2024 Graduation Examination Secondary 4E Pure Physics (6091) MARKING SCHEME Paper 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 B D D D A B C B B C A C A B A C D B C C 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 C D C B B B A A D A C B D A C B A D D A Paper 2 Section A Question Answer Mark s Markers’ Comments 1 (a) random error B1 (b) Digital vernier calliper. Degree of accuracy is 0.01 mm B1 B1 (c) volume =mass ÷ density = 1380 ÷ 7.65 = 180 cm3 A1 2 (ai) B1 B1 Correct labeling/Directio n of forces (aii) 30 – T = 3a T – 20 = 2a a = 2 m/s2 M1 A1 (b) Applying Principle of Energy Conservation, magha = ½ mav2 + mbghb hb = 10.8 m M1 A1 3 (a) moment of weight = weight ×perpendicular distance of weight from pivot = 150 ×1.8 = 270 Nm A1 (bi) The Principle of Moments states that when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point. B1

2 Question Answer Mark s Markers’ Comments (bii)  By M = Fd  Higher perpendicular distance  increase ACW moment  By POM  for the same distance of the weight of the barrier  an additional force is needed to increase the CW moment to balance thr barrier. B1 B1 4 (a) Choose two factors: density of water/ gravitational field strength/depth of water Accept temperate and humidity of air (b) P = hρg + Patm 3x105 = h(1030)(10) + 1x105 h = 19.4 m M1 A1 (ci) Correct arrangement of LDR and light bulb (Parallel) B1 0 mark if no labelling (cii) Deeper  darker  brightness decreases  resistance of LDR increases  Voltage of LDR increase due to potential dividing Light bulb parallel to LDR  voltage increases  P increases  brighter B1 B1 5 (a) from elastic potential store to kinetic store and gravitational potential store B1 (b) kinetic store and gravitational potential store to gravitational potential store and elastic potential store B1 6 (a) Cooling Evaporated ethanol gain latent heat in the form of PE to change state  remove thermal energy from skin B1 B1 (b) Rate increases. Moving air remove evaporated ethanol particles so that other ethanol particles can leave the body easily B1 B1 7 (a) ultraviolet rays, X-rays B1 (b) detection and treatment of cancer OR imaging/gamma photography OR telescopes OR sterilisation of food/medical equipment B1 (c)  radiations arrive) at same time.  because they have same speed in a vacuum B1 B1 8 (a) sin c = 1 / refractive index c = 48.8° A1 (b) B1 Correct path of light / angles labelled correctly

3 Question Answer Mark s Markers’ Comments (c) i > c and light travels from optically denser to less dense medium  TIR occurs B1 9 (a)  Correct ray A and B drawn with arrows  Image drawn correct at 2F B1 B1 (b) Co