PHS 2024 4Exp PP Prelim P1 worked solution (shared)

1 [Turn Over PRESBYTERIAN HIGH SCHOOL SCIENCE DEPARTMENT MARKSCHEME Subject: Physics Test: PrelimExam Setter: Year: 2024 Level: Sec 4 Express Answers to Paper 1: MCQ 1 C 2 D Fall at a constant acceleration of 10 m/s2 All objects will fall at the same rate if there is no air resistance. 3 C • greater mass • greater weight • accelerates longer before air resistance balances with the weight • take longer time to teach terminal velocity • higher terminal velocity 4 A gb = 9.81 N/kg gt = 9.79 N/kg Wb = mgb 600 = m(9.81) m = 61.2 kg Wt = mgt = (61.2)(9.79) = 599 N 5 B When  = 180° , magnitude of resultant force = 4 + ( -2) = 2 N When  = 90° , magnitude of resultant force = √(22 + 42) = 4.47 N When  = 0° , magnitude of resultant force = 4 + 2 = 6 N For resultant of 4N, 90° <  < 180° 6 A Resultant force, F = ma From graph : 1st Part: F , acceleration  Since gradient of v-t graph = acceleration When acceleration , gradient of graph  From graph : 2nd Part: F is zero, acceleration is zero Since gradient of v-t graph = acceleration When acceleration is zero, gradient of graph is zero or constant speed

2 7 A Volume of water = 150 – 100 = 50 cm3 Mass of water = 50 × 1.0 = 50 g Mass of paraffin = 0.80 × 100 = 80 g Total mass = 50 + 80 = 130 g 8 A (G.P.E)A + (K.E)A = (G.P.E)B + (K.E)B + W.D against friction (2)(10)(2) = ½ (2) v2 + 2.6 × 4 v = 5.4 m/s 9 B In an area of 1.0 m2 of each panel receives 0.80 kJ of energy from the Sun in 1.0 s. Power input for 1.0 m2 = energy/time = 0.80 kJ / 1.0 s = 0.80 kW Power input for 7.2 m2 = 0.80 kW × 7.2 = 5.76 kW Efficiency = 1.0 kW/ 5.76 kW × 100% = 17% 10 A chemical energy is transferred electrically to the internal store and kinetic store. 11 A The pollen particles are being bombarded by the heavier particles of the water. 12 C P gas - P atm = 30 cm Hg P gas = 30 cm of water + 76 cm Hg = (0.3)(1000)(10) + (0.76)(13 600)(10) = 106 360 Pa = 106 000 Pa 13 D Pressure at X = Pressure at Y Since height of liquid X is greater than liquid Y, therefore density of liquid X is smaller than density of liquid Y. 14 C For the energy to be transferred only by radiation, it must be in a vacuum as conduction and convection require a medium for energy to be transferred. 15 C High Heat Capacity --→ more change in internal energy is needed to change the temperature -→ temperature increase at slower rate. Since for Y, the rate of increase in temperature is the slowest, it has the largest specific heat capacity. 16 A One bucket contains 5 kg of water at 20 °C and the other contains 1 kg of water at 80 °C. Let the final temperature be . internal energy lost by 1 kg of water = internal energy gained by 5 kg of water (1) c (80 - ) = 5 c (  - 20) 80c -  = 5 - 100  = 30 °C

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