2024 JVS Physics Prelim P1&2 marking scheme

Jurongville Secondary School Science Department 2024 Marking Scheme Assessment: Physics Preliminary Examinations Level: Sec 4 Exp Paper 1 Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans Qn Ans 1 D 2 D 3 D 4 B 5 A 6 A 7 B 8 C 9 B 10 B 11 C 12 A 13 D 14 C 15 B 16 C 17 C 18 C 19 B 20 D 21 D 22 B 23 D 24 A 25 B 26 A 27 D 28 A 29 C 30 C 31 A 32 C 33 A 34 A 35 D 36 D 37 B 38 A 39 C 40 B

Qn Marking Scheme Remarks Marks 1(a) 1(b) 1(c) Acceleration due to gravity = 10.0 (6.0 – 0) / t = 10.0 t = 6.0 / 10.0 = 0.6 s Height = Area under velocity-time graph = ½ (0.6)(6) = 1.8 m Correct working Correct answer and unit Each correct straight line Allow for ecf from (a) Correct working Correct answer and unit Allow for ecf from (a) C1 A1 B1, B1 C1 A1 0.2 0 0.6 6 time / s 0.8 1.0 1.2 0.4 4 2 -6 -2 -4 0.0 m / s velocity

Qn Marking Scheme Remarks Marks 2(a) 2(b) Scale 1 cm rep 5 N Magnitude of wind force = 42 N ± 0.5 N Direction of wind force = 26° clockwise from the horizontal Mass of kite = 5 / 10 = 0.5 kg Resultant force = m a 42 = 0.5 x a a = 42 / 0.5 = 84 m/s2 Correct diagram with arrows Appropriate scale Correct magnitude Correct angle Correct working Correct answer and unit Allow for ecf from (a) B1 B1 B1 C1 A1 3(a) 3(b) 3(c) The load is placed vertically above support B. The perpendicular distance between the load and support B is zero. Thus there is no moment about support B. Taking moments about support B, Force at support A x 1.4 = (24)(1.4 / 2) Force at support A = 16.8 / 1.4 = 12 N For maximum distance that load can move to the right, the weight of plank just balance the load at support B and no force at support A. Taking moments about support B 76 x Maximum distance that load can move to the right = (24)(1.4 / 2) Maximum distance that load can move to the right = 16.8 / 76 = 0.22 m OWTTE Correct working Correct answer and unit Correct working Correct answer and unit B1 C1 A1 C1 A1 4(a) 4(b) 4(c) Pressure is the force per unit area. Pressure = Force / Area 23000 = 29 x 10 / Area Area = 290 / 23000 = 0.126 m2 Pressure in gas cylinder + 13600 x 10 x (0.059 – 0.035) = 100000 Pressure in gas cylinder = 100000 – 3264 = 96736 = 96700 Pa (3 s.f.) OWTTE Correct working Correct answer and unit Correct working Correct answer and unit B1 C1 A1 C1 A1 weight of kite tension of string resultant force

Qn Marking Scheme Remarks Marks 5(a) 5(b) 5(c)(i) 5(c) (ii) There dust particles moving faster means that there is an increase in its kinetic store/energy. This means that there is an increase in the temperature of the gas. An electric heater used to heat room air is placed on the floor to ensure convection currents to take place in the room. The air near the heater becomes hot and is less dense. The hot air rises and cold air in the room sinks. This causes convection current to take place. The specific latent heat of vaporization of a substance is the amount of energy required to change 1 kg of the substance from liquid to gas, or vice versa, without any change in temperature. Power x time = energy gain by pot + energy gain by water 2000 x t = 1.2 x 445 x (120 – 30) + 3.0 x 4200 x (100 – 30) + 0.5 x 2.3 x 106 t = (48060 + 882000 + 1150000) / 2000 = 1040 s = 17.3 min OWTTE OWTTE OWTTE Correct working Correct answer and unit B1 B1 B1 B1 B1 C1 A1 6(a) 6(b) 6(c) Sound is produced by the vibration of air particles around the vibrating violin string. A series of compression and rarefaction pressure regions forming longitudinal waves transmit sound by vibrating air particles. Speed of sound = wavelength / period = 1.2 / 0.002 = 600 m/s OWTTE Wave is twice amplitude of original wave Wave frequency is twice of original wave Correct working Correct answer and unit B1 B1 B1 B1 C1 A1

Qn Marking Scheme Remarks Marks 7(a) 7(b) 7(c) 7(d) Effective resistance when circuit is in a dark and hot room = [1 / (100 + 15000) + 1 / (300 + 50)]-1 = 342 Ω Current in battery = 12 / 342 = 0.0351 A The current flow in the battery will be largest when the circuit is in a bright and hot room. This is because the effective resistance of the circuit is the lowest. Potential difference across LDR = [12 / (100 + 400)](400) = 9.6 V The current flow in the LDR is not affected by the resistance of the thermistor since the LDR and thermistor are connected in parallel. Correct working Correct answer and unit OWTTE Correct answer and unit OWTTE C1 A1 B1 B1 B1 B1 8(a) 8(b) 8(c) The three-pin plug is necessary because the oven has exposed metal parts. If there is a fault, the metal parts may become live and the earth wire in the three-pin plug will provide a low resistance path for current to flow and protect the user. The fuse has a resistance wire that only allows certain amount of current to flow through it. It will melt and stop current flow if current exceed the allowed current in the fuse. It is connected in the live wire. Current = Power / Voltage = 800 / 240 = 3.33 A The 5 A fuse is selected as it is slightly above 3.33 A OWTTE OWTTE Correct working Correct answer B1 B1 B1 B1 B1 9(a) 9(b) 9(c) Hard magnetic materials is not easily magnetized but does not lose magnetism easily once it is magnetized Soft magnetic materials can be easily magnetized but loses magnetism easily. This is because soft iron would concentrate the magnetic field from the coils of wires for a stronger magnetic field. The function of the commutator is the to change the contact from one brush to the other. This would reverse the direction of current in the coil and ensure the coil rotate in one direction. OWTTE OWTTE OWTTE B1 B1 B1 B1 B1

Qn Marking Scheme Remarks Marks 10(a) 10(b) 10(c) 10(d) 10(e) 10(f)(i) 10(f)(ii) Nuclear decay is a random process which an unstable atomic nucleus loses its energy by emission of electromagnetic radiation or particles. Nuclear fission is a process in which the nucleus of an atom splits and releases a large amount of energy while nuclear fusion is a process in which two atomic nuclei combine to form a heavier nucleus and releases a large amount of energy. Half-life = 29 years The Geiger-Muller counter will detect the amount of strontium-90 that is able to pass through the steel sheet. If the counter detects too much radiation, that means the steel sheet is too thin. If the counter detects less than normal radiation, that means the steel sheet is too thick. 1. The radioactive substance could be contained in a thick lead / concrete container. 2. Remote controlled devices can be used to move the radioactive substances. CAO OWTTE Correct nuclide notation of yttrium Correct nuclide notation for beta particle OWTTE Correct plotted points and best fit curve Line on graph to determine half - life OWTTE Any two suitable ways B1 B1 B1 B1 B1 B1 B1 B1 B1 B1 B1 B1 90 38