Tiêu đề 2024 GCE A level H2 Physics 9749 Ans.pdf ✅

2 1 Ans: A Key concept: Knowledge of prefixes. Mm here means mega-metre, which means 106 m. Hence, 4 × 102 Mm = 4 × 108 m. Area = πr 2 = π(4 × 108 ) 2 = 5 × 1017 m2 . Next, Gm2 really means (Gm)2 = (109 m)2 = 1018 m2 , while Tm2 = (Tm)2 = 1024 m2 . Hence, area = 5 × 1017 m2 = 5 × 10-1 Gm2 2 Ans: B Key concept: Acceleration is gradient of v-t. For first part, • a is constant and positive. • Hence, gradient of v-t is constant and positive. For second part, • a is constant and negative. • Hence, gradient of v-t is constant and negative. 3 Ans: C Key concept: sy = 0 when the ball leaves and lands some time later. sy = uyt + 1⁄2 ayt 2 0 = (15 sin 40°)t + 1⁄2 (−1.62)t2 t = 11.9 s 4 Ans: B Key concept: Equilibrium means closed vector triangle in the same orientation + normal contact forces are directed away and perpendicular to surface. 5 Ans: D Key concept: Hooke’s Law. Initially, W is distributed between all 3 springs. Hence, tension in each spring = W/3. Hence, kx = W/3 and k = W/3x Finally, 2W is distributed between 2 springs, Hence, kx2 = W and x2 = W ÷ (W/3x) = 3x 6 Ans: B Key concept: Hooke’s Law (permanent deformation). When spring is extended, positive work done = gain in Elastic PE. If spring can be recovered to original length, the elastic PE can be recovered back (as negative work done). Hence, net work done = 0 J. In this question, there is a permanent deformation. Hence, part of the positive work done on the spring during extension is to do work to cause permanent deformation (and is not recoverable), and this is characterised by area OPRS (which represent the net work done) 7 Ans: C Key concept: Power = Driving force × velocity Take note that the “total resistive force” does not include component of weight downslope (you can deduce this from the fact that the component of weight > 600 N). At constant speed, forward driving force = mg sin 10° + 600 Power = (mg sin 10° + 600)(16) = 34.1 kW.
3 8 Ans: D Key concept: Positive work done on gas during compression (volume decreases) In this question, they are referring to the positive work done on gas (not explicitly mentioned but you are expected to be able to infer so) Positive work done on gas is only during compression. Hence, RS and SP. 9 Ans: A Key concept: arc length = rθ and ω = ∆θ / ∆t. l = rθ, hence θ = l / r Hence, ω = (l / r) ÷ t = l / rt 10 Ans: A Key concept: centripetal acceleration = rω2 Centripetal acceleration = (0.65 × 107 )(2π / (24 × 3600))2 = 0.034 m s-2 . Centripetal acceleration is always directed towards the centre of the circular motion (i.e. centre of Earth) 11 Ans: A Key concept: Magnitude in the question really means absolute values. From the graph, it is clear that both absolute values of the potential decreases, and the difference between potential decreases as well as distance increases. 12 Ans: A Key concept: Average force = change in momentum / time between collisions (derivation of pressure of gas). Change in momentum = mv – (– mv) = 2mv Time between collision = distance to and fro / speed = 2x / v Average force = 2mv / (2x / v) = mv2 / x 13 Ans: D Key concept: Specific heat capacity and equilibrium temperature Loss in heat of V = Gain in heat of V/4 m1C(60 – T) = m2C(T – 20) (ρV)(60 – T) = (ρ × 1⁄4 V)(T – 20) T = 52 °C