Serangoon_Gardens_2022 4N_Phy_Prelim_MS

1 Serangoon Garden Secondary School 4NA Science(Physics) (5105) Prelim 2022 Mark Scheme PAPER 1 Qn Ans Explanation 1 C 2 B Reading on vernier scale = 1.56 cm Diameter of one ball bearing = 1.56 cm / 3 = 0.52 cm 3 D Speed is represented by the gradient (slope or steepness) of a distance-time graph Consider how in option D, the distance increases by the same amount every second. 4 C FR = 4000 – 1000 = 3000 N a = FR / m = 3000 / 1200 = 2.5 m/s2 5 C 6 C 7 C The piston moves to the right because the air expands. The air expands because the molecules move about faster and further apart. The molecules do not change in size. The molecules also do not increase in number, as it is a sealed cylinder. 8 B As the ice continues to be heated, it continues to gain thermal energy. The thermal energy gained is used to overcome the forces of attraction between molecules. The molecules do not gain kinetic energy, hence there is no change to the temperature of the ice.

2 9 D 10 D The temperature of the liquid decreases because of evaporation. When the more energetic particles in the liquid escape into the air, it leaves behind the less energetic particles. This decreases the average kinetic energy of the particles in the liquid. 11 A 12 B Distance between 2 successive wavefronts is one wavelength. Hence, X to Y is two wavelengths. One wavelength = 1.6 cm / 2 = 0.8 cm 13 C 14 C All EM waves travel at the speed of light! 15 B Speed = distance travelled / time taken = (400 x 2) / 2.5 = 320 m/s (distance travelled is 400 x 2 because the sound travels to the wall and back in 2.5 s!) 16 B Conventional current flows from positive to negative. Electron flow flows from negative to positive (electrons are repelled from negative terminal of battery and attracted towards positive terminal) 17 C In a series circuit, sum of p.d. across components = p.d. across whole circuit (e.m.f. of battery) p.d. across identical resistors are the same (in a series circuit). So, Vresistor + Vlightbulb + Vresistor = Vemf 1.0 + Vlightbulb + 1.0 = 6.0 Vlightbulb = 6.0 – 2.0 = 4.0 V

3 18 D First, find p.d. across 4.0 Ω branch: V = RI = (4.0)(1.0) = 4.0 V Since p.d. across parallel branches are equal, p.d. across 2.0 Ω resistor = 4.0 V so, I2.0Ω = V / R = 4.0 / 2.0 = 2.0 A 19 C 20 B The fuse must be connected to the live wire! PAPER 2: Section A Question Answer Marks 1 (a) (i) 4.0 m/s 1 (ii) 8.0 m/s 1 (b) Speed decreases at an increasing rate OR Increasing deceleration 1 (c) Distance travelled = area under speed-time graph = ½ x 5.0 x 8.0 = 20 m 1 1