2024 SNGS Physics Prelim P2 MS

1 2024 S4 Physics Prelim P2 Answer unit penalty: deduct [1] per incorrect or missing unit. s.f. penalty: least s.f. or plus one unless stated otherwise. deduct [1] per paper. Section A Qn Ans Marks 1(a) Speed is a scalar with only magnitude. Velocity is a vector with both magnitude and direction. speed is scalar and velocity is a vector. [not acceptable, require explanation] define speed and define velocity. [not acceptable] B1 1(b)(i) 4.5 s (accept 4.3 – 4.6 s) A1 1(b)(ii) The firework is moving upwards from 0 to 4.5 s with decreasing velocity. (It reaches the highest point at 4.5 s) It is moving downwards after 4.5 s. [note: graph shows only 5.0s of motion] ecf for timing using b(i) answer B1 B1 1(c) 10 m/s2, downward 10 m/s2, downward [note: the misconception] units is a must. cannot be negative. B1 B1 1(d) Draw the resultant correctly (with label R) Resultant = 5.5 x 10 = 55 m/s (to correct sf) (acceptable 54 – 57 m/s) maximum 1 mark for part (d) if no double arrow for resultant velocity M1 A1 2(a) Gravitational force acting on Earth by the barrel. B1 2(b)(i) Work done = mgh = 14 x 10 x 3.2 = 450 J (2 sf) A1 R

2 2(b)(ii) Energy is transferred mechanically by a force from the chemical potential store of the farmer to the gravitational potential store of the barrel. note: accept no mention of store eg. chemical potential energy to gravitational potential energy B1 2(c)(i) P = WD/t 75 = 450/ t t = 6.0 s B1 B1 2(c)(ii) taking downwards as positive, W = mg = 140 N Resultant force = ma = 7.0 N 140 – Fu = 14 x 0.50 Fu = 133 N = 130 N (2 sf) M1 A1 3(a) Water near the base is heated and expands and becomes less dense than the surroundings. The heated water rises and the cooler denser water at the top falls. Convection currents set up. B1 B1 3(b)(i) Wood is a poor conductor of heat. Slow down rate of heat transfer (to handle) accept: thermal insulator B1 3(b)(ii) Shiny surface is a poor emitter of infrared radiation annotate if student did not mention IR (do not accept reflector, absorber) B1 3(b)(iii) Copper is a good conductor of heat. Allows transfer of energy to water through heating. B1 4(a) Speed of light Decreases B1 B1 4(b)(i) Draw a normal at E, label with X B1 4(b)(ii) Read c correctly n = 1/ sin c = 1/ sin 45 = 1.4 (2 sf) allow ecf from 4(b)(i) C1 A1 4(b)(iii) Angle of incidence at AC is greater than critical angle. Total internal reflection occurs at E and there is no longer any ray travelling along EC. (describe) B1 4(c)(i) Obeys laws of reflection (accept other properties found in the textbook eg transverse waves) (not acceptable to mention ‘does not require medium’) B1

3 4(c)(ii) V = f 3.0 x 108 = f (690 x 10-9) f = 4.3 x 1014 Hz M1 A1 5(a) I varies linearly with V (resi