EJC 2022 Prelim P2 Guide

©EJC 2020 9749/J2H2JCT/2020 EUNOIA JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATIONS 2022 General Certificate of Education Advanced Level Higher 2 PHYSICS MARK SCHEME 9749 August/September 2022 Paper 2 Structured Questions Qns Answer Marks 1(a) Forces must be labelled forces clearly in full – Weight, Reaction Force, Tension Lines of action forces (including intersection of the 3 lines) must be clearly shown. 1 (b) Let T be the tension in the spring. Taking moments about A, Sum of clockwise moment = Sum of anticlockwise moment mg (0.20 cos30°) = T (0.40) 1.2(9.81) (0.20 cos30°) = T (0.40) T = 5.10 N 1 1

2 ©EJC 2022 9749/J2H2Prelim/2022 Qns Answer Marks (c) Let Rx and Ry be the horizontal and vertical components of the reaction force R. Resolving forces horizontally, Rx = T cos 60° = 5.10 cos 60° = 2.55 N Resolving forces vertically, Ry + Tsin 60° = W Ry + 5.10 sin 60°= (1.2)(9.81) Ry = 7.36 N 22 XY 22 magnitude of reaction force 2.55 7.36 7.79 N RR R+ =+ = = 1 1 1 (c) increase (stiffer spring so a smaller extension needed for the same elastic force, resulting in larger angle) 1 Ry Rx

3 ©EJC 2022 9749/J2H2Prelim/2022 [Turn over Qns Answer Marks 2(a)(i) Total momentum of an isolated system of interacting bodies before and after collision remains constant if no net external force acts on the system. 1 (a)(ii) Presence of external force like weight / force from the ground 1 (b) By Conservation of Energy, loss of gravitational potential energy = gain in kinetic energy m 1 2gh m= ( )( ) 2 1 2 2 9.81 2 2 . . 0 6 6 m s v v gh −= = = 1 (c) collision is elastic, total KE before and after bounce conserved ½ (0.8)(6.26)2 = ½ (0.3)(v2) + ½ (0.5)(3.2)2 v = 9.35 m s-1 1 1

4 ©EJC 2022 9749/J2H2Prelim/2022 Qns Answer Marks 3(a)(i) Since the direction of field strength is directed upwards at point O, the horizontal component of the electric field strength due to the 2 charges at O are equal in magnitude and opposite in direction. oo12 22 o 1 o 2 sin 30 sin 6044 sin 60 1.73 sin 30 1.7 oo qq rr q q   = == = 1 3(a)(ii) correct shape, graph does not touch the y-axis or dotted line (else max 1) E = 0 at position nearer to Y Relative field strength at X larger in magnitude than at Y 1 1 3(b)(i) electric field strength is a vector quantity Since the resultant field strength at point O is directed upwards, the resultant electric field strength is the vector sum of the vertical com