SCGS 2024 PHY PRELIM P1+P2 MS

2024 PRELIM PHYSICS SUGGESTED ANSWER SCHEME PAPER 1 (40 marks) Qn Answer Explanation 1 B The clay will displace the same volume when it is placed in the bigger cylinder. 2 C Mass is unchanged, thus A & D is incorrect. Weight at both points are different as the acceleration of free fall is different, thus B is incorrect. 3 C By Pythagoras theorem, only C and D is possible. To construct a right-angle triangle at the point where the two cords meet, F2 has to be the larger force (8 N). 4 B Since the routes have different distances, average speeds for both are different. Displacement is the same from P to R even though distances are not equal. 5 A Calculating the area above the time axis: On Earth, height = ½ (1.2)(12)m=7.2 m ; On Mars, height= ½ (3.2)(12) m = 19.2 m Thus height difference = 12 m 6 B Total displacement = (+3.0 x 10)m + (-6.0 x 5)m = 0.0 m Average velocity = 0.0 m /15s = 0.0 ms-1 7 B A, B and C all demonstrates forces acting on the SAME body. 8 A Gravitational potential store = mgh⇒ h = Gravitational potential store / mg. Thus h ∝ 1/ m 9 C A and B are incorrect as there is no net work done since the suitcase is stationary. On the slide, work is not done on the suitcase – the suitcase slides down due to its own weight. C – work is done on it to raise it up by 10 m. 10 C Rate of increase in the kinetic store = (500 – 200)x 103 N x 40 ms-1 = 12 x 106 W 11 C Taking moments about the pivot, 0.43 N x (6 -2.4) cm = W x 1.2 cm W = 1.3 N 12 C Centre of gravity has to be at the pivot for the object to be at neutral equilibrium. 13 B Pressure of the gas = pressure due to piston + Atmospheric pressure 1.2 x 105 Pa = (4.0 x 10)/A + 1.0 x 105 Pa A = 2.0 x 10-3 m2 14 A Adding mercury to the trough will not affect the height h which is a measure of the atmospheric pressure. 15 C Since temperature remains constant, the average speed of the gas molecules remain constant. However, when compressed the density of the gas increases and hence the frequency of collisions of the gas molecules with the walls of the container increases. 16 B When air is sucked out, the pressure inside the packet drink decreased as the number of air molecules per unit volume in the packet decreased due to the decrease in the frequency of collision of the air molecules on the packet wall. 17 A B is incorrect as heat transfer is unidirectional and there is no such concepts as coldness. C’s description is heat transfer is via convection and not radiation. At thermal equilibrium there is no NET flow of thermal energy but thermal energy exchange is continuous. 18 B When water changes state from liquid to solid, the particles have to come closer together by losing internal energy and hence their average potential energy decreases due to the closer average distance between the molecules. 19 C Thermal energy supplied to X = Thermal energy supplied to Y (Cx) 𝜃 = (Cy) 2𝜃 Cx = 2 Cy 20 A Therm