2023 AHS Physics Prelim Paper 1 solutions

AHS 2023 S4 Physics Prelim Exam Paper 1 solutions Q Ans Explanation 1 C diameter of Earth = 10 x 106 m = 1.0 x 107 m = 1.0 x 104 x 103 m = 1.0 x 104 km diameter of atom = 10 x 10-9 m = 1.0 x 10-1 x 10-9 m = 1.0 x 10-1 m length of football field = 100 m = 10 x 101 m 2 B From P to Q to R → ¾ of a complete oscillation period of oscillation = (1.5 / 3) x 4 = 2.0 s number of oscillations in one minute = 60 / 2.0 = 30 3 A 4 D Since velocity is positive throughout, there is no change in direction. Option B and C can be eliminated. Before opening his parachute, the velocity should not decrease for the parachutist. 5 B Distance travelled from t = 20 s to t = 50 s = area under the graph = (½ x 20 x (12.0 + 16.0)) + (½ x 10 x 12.0) = 340 m. Average speed = total distance / total time = 340 / 30 = 11.333…. = 11 m / s (2 s.f.) 6 A There are no action-reaction pair as all the forces are acting on the same ladder. 7 D The block of wood is moving to the left. Hence forces acting towards the left is positive. First 5.0 s: Using “F = ma”, since a = 0 m / s2, net force = 0 N Thus, there must be friction of 20 N acting on the wood. After 5.0 s: Net force = F = F1 – friction – F2 = 20 N – 20 N – 10N = - 10 N (this means the net force is acting to the right, opposite to the motion of the wood) From “F = ma”, ‘a’ is negative when net force F is negative. Negative ‘a’ means deceleration. 30 N South 30 N West Combined effect of 2 horizontal forces = 30 N West Together with the 30 N South force, the resultant force is acting approximately in the South-West direction. Hence to keep the mass in equilibrium, an additional force with the same magnitude as the resultant force acting in the opposite direction to the resultant force is required. Resultant force South-West Additional force North-East

8 C Using “ ρ = m / V ” V of each ball bearing = m / ρ = 18.0 / 9.0 = 2.0 cm3 V of eight steel balls = 2.0 x 8 = 16.0 cm3 Reading on measuring cylinder = 25.0 + 16.0 = 41.0 cm3 9 D d4 is perpendicular to the line of action of the force F. 10 D Diagram Taking moments about K, sum of clockwise moments = sum of anti-clockwise moments (11.0 x 3.0) + (11.0 x 1.2) = (12.0 x d) + (10.0 x 1.5) d = 31.2 / 12.0 = 2.6 m 11 C Pressure in the mercury column increases with depth. Atmospheric pressure is acting on the surface of the mercury. So the point is 10 cm above the surface of the mercury. 12 B Liquid pressure is only affected by height of the liquid column above it, not on volume, cross-sectional area or shape of column. See textbook page 128. 13 B liquid pressure difference in mercury column = Δh ρ g = (6.0 / 100) x 13600 x 10