RVHS_H2_Physics_P3_Soln

River Valley High School Pg 1 of 9 JC 2 H2 Physics 9749 Preliminary Examinations 2024 RVHS JC2 H2 Physics Prelim Examination 3 Mark Scheme 1 (a) (i) time = 0.43 / 1.1 = 0.39(1) s A1 (ii) 𝑠 = 𝑢𝑡 + 1 2 𝑎𝑡2 = 1 2 (9.81)(0.39)2 C1 = 0.75(0) m A1 (iii) vertical velocity: 𝑣 = 𝑢 + 𝑎𝑡 = (9.81)(0.39) = 3.8259 m s-1 M1 𝜃 = 𝑡𝑎𝑛−1 𝑣𝑦 𝑣𝑥 = 𝑡𝑎𝑛−1 3.8259 1.1 = 74(.0)° A1 (iv) 1. Horizontal line at a non-zero value of a. B1 2. Curved line from origin with increasing gradient B1 (b) acceleration of free fall is unchanged / not dependent on mass and so no effect (on time taken) A1 2 (a) 12 and TT : down 3T : up B1 (b) By Principle of Moments, Taking moment about the pivot at the base of wire 1, sum of clockwise moments = sum of anti-clockwise moments ( )( ) ( ) ( ) ( )( ) 3 3 3 14 5 10 0 14 5 350 10 9 8110 0 49 14 5 10 0 8 N p p . . Tmg . mg . .. . T . − = = = = M1 A1 (c) P is in vertical translational equilibrium, R adds additional downward force. 3T is only upward force and so must provide additional tension, more likely to snap. B1 All 3 must be correct.

River Valley High School Pg 2 of 9 JC 2 H2 Physics 9749 Preliminary Examinations 2024 If method involves principle of moments, reference to a pivot must be made known before a mark can be awarded together with the reasoning. 3 (a) loss in GPE = gain in elastic PE 2 22 1 2 (25)(0.050) 0.028959 kg2 2(9.81)(0.110) 0.029 kg(shown) mgh kx kxm gh = = = = = M1 (b) When the spring first compresses, the magnitude of the force from the spring is less than weight. Hence, there is still a downward resultant force that causes the marble to continue accelerating. B1 B1 (c) Max speed of marble happens when force from spring = weight 22 (0.028959)(9.81) 0.01136 m25 11 (25)(0.01136) 0.001614 J22 (0.060 0.01136) (0.028959)(9.81)(0.060 0.01136) 0.02027 J 0.02027 0.001614 0.0 kx mg mgx k gain in EPE kx loss in GPE mg gain in KE loss in GPE gain in EPE = = = = = = = =+ = + = =− =− = 19 J (2sf) M1 M1 M1 A1 4 (a) When a charged particle is travelling in a magnetic field, it experiences a magnetic force that is always perpendicular to its velocity (and the magnetic field lines). Since the charged particle is travelling perpendicular to the uniform magnetic field, and that the resultant force only consists of the magnetic force, the particle travels in a circular path. B1 B1 (b) centripetal force provided by magnetic force M1 M1

River Valley High School Pg 3 of 9 JC 2 H2 Physics 9749 Preliminary Examinations 2024 2 2 2 2 2 mr Bqv vm Bq r m Bq Bq m Bq Tm mT Bq       = =  = = = = A1 (b) magnetic force provides for centripetal force 2 26 5 19 (4.5 10 )(4.8 10 ) 0.60(0.15) 2 4.8 10 mvBqv r mvq Br C − − = ==   = M1 A1 5