Tiêu đề 2019 GCE A level H2 Physics 9749 Ans.pdf ✅

H2 Physics Nov 2019 GCE A-Level Solutions Paper 1
Paper 1 1. Ans: D 2. 1% of uncertainty = 1/100 (4.072) = 0.0407 V Total uncertainty = 0.0407 +0.01 = 0.05072 V = 0.05 V (1 sf) V = 4.07 (to follow dp of uncertainty)  0.05 V Ans: D 3. Let the entire distance fallen be s in time t. Initial velocity u = 0 Using s = ut + 1⁄2 at2 s = 1⁄2 gt2 --- (1) 0.25 s = 1⁄2 g (t - 1) 2 --- (2) Solving simultaneous equations, t = 2 s Ans: D 4. When air resistance is present, speed increases, acceleration decreases (as Fnet decreases due to increase in air resistance) Ans: C 5. COM: Pi = Pf (Pi = 0) The total momentum of the system is zero, velocity of the centre of gravity of the system does not change. C.G does not move. Ans: A 6. KEi = 1⁄2 m u2 ---- (1) KEf = 1⁄2 mv2 + 1⁄2 (m)(2v)2 --- (2) By COM, mu = mv + 2mv v = 1/3 u --- (3) Sub (3) into (2) KEf = ହ ଵ଼ mu2 Fraction lost = (KEi – KEf ) /KEi = ( 1⁄2 m u2 - ହ ଵ଼ mu2 ) / 1⁄2 m u2 = ସ ଵ଼ m u2 / 1⁄2 m u2 = ସ ଽ Ans: B 7. WD = area under F-x graph = 1⁄2 (20 x 10-3 )(28) = 0.28 J Ans: A  Relatively easy questions: 1,4,7,9,10,11,12,14,16,19,20,22,25,27  Relatively challenging questions: 5,13,23 and 24
8. v 2 = u2 + 2as v 2 = 2as KE = 1⁄2 mv2 =mas. --- (1) Fnet = W - Wsin ma = mg (1 - sin) a = g (1 - sin) --- (2) As  increases when the object moves up the slope, a decrease Plot KE against s, gradient = ma. [From (1)] Thus, gradient is decreasing. Note: Some students think KE is decreasing not realising that a force is applied to the object continuously. Ans: D 9. P = WD/t = mgh /t = [(1.3x109 ) (9.81) (2) ] /24 x 60 x 60 = 300 kW Ans: D 10. v = R  = v/R, plot graph of  against R with constant v. Ans: B 11. a = r2 where r = 7m, a = 20 (9.81)  = 5.3 rad s-1 Ans: D 12. By COE, KE + GPE at surface = KE + GPE at infinity 1⁄2 mv2 – GMm/R = 0 v = (2GM/R)1/2 Ans: A 13. 1⁄2 m = 3/2 kT When molar mass = 4 g = 0.004 kg, T = (30 +273.15) K 1⁄2 mmolar = 3/2 RT c = (3RT/mmolar) 1/2 = 1400 m/s Ans: C F = W W 