2023 JPJC Prelim H2 Phy P3 Solutions

2023/JPJC/Prelim/9749/03 [Turn over Answers to 2023 JC2 Preliminary Examination Paper 3 (H2 Physics) Suggested Solutions: No. Solution Remarks 1(a)(i) horizontal component 1 67cos14 65.01 65.0 m s− = = ≈  vertical component 1 67sin14 16.21 16.2 m s− = = ≈  [1] for correct answer [1] for correct answer 1(a)(ii) horizontal displacement 65.01 4.9 318.5 319 m = × = ≈ [1] for correct substitution and answer 1(a)(iii) Using 2 yy y 1 2s ut at= + , Taking downward as positive, ( )( ) ( )( ) 2 y 116.21 4.9 9.81 4.92 38.34 38.3 m s = −+ = ≈ [1] for correct substitution [1] for correct answer 1(a)(iv) angle of the slope to the horizontal 1 38.34tan 318.5 6.864 6.86 θ − =  = ≈  [1] for correct substitution [1] for correct answer 1(b)(i) [1] for correct new path Note: new path under present path new path

2 2023/JPJC/Prelim/9749/03 No. Solution Remarks 1(b)(ii)1. The path of the ball at the start is determined by the direction of the force of the club acting on the ball or air resistance has acted only for a short period of time. [1] for correct answer 1(b)(ii)2. The horizontal velocity is much reduced by air resistance. [1] for correct answer 2(a)(i) Gravitational force on satellite provides for centripetal force to keep satellite in orbit. 2 2 2 2 23 2 63 11 24 2 44 10(9.0 ) (6.67 )(5.97 10 1 50 0 ) 80 ES S E E GM M Mr r GM r Tr rT GM s ω π ππ − = =  = = ×  × = × [1] correct substitution [1] correct answer 2(a)(ii) Work done = increase in total energy of satellite ,, 11 24 76 9 22 (6.67 )( 10 10 1 5.97 )(500) 1 1 2 1.0 0 10 9.0 1.1 J10 Tf Ti Es Es fi EE GM M GM M rr − = −  =− −−    = −+ × = ×× ×× [1] correct substitution [1] correct answer 2(b)(i) The gravitational force acts towards centre of Earth provides the centripetal force and thus, gravitational force must lie on the plane of orbit which passes through centre of Earth. Additionally, in order for the satellite to orbit such that it remains at a fixed relative position above the Earth, its axis of rotation must coincide with Earth’s axis of rotation and thus it has to orbit in the equatorial plane. [1] [1] [1] 2(b)(ii) Geostationary satellites move in orbits where they are at a fixed relative position above the Earth. This allows the satellites to constantly receive and transmit telecommunication signals to and from the same position on the Earth’s surface. [1] 3(a)(i) The internal energy of a system is the sum of a random distribution of kinetic and potential energies associated with the molecules of a system. [1]

3 2023/JPJC/Prelim/9749/03 [Turn over No. Solution Remarks 3(a)(ii) UQW∆=+ U∆ – increase in internal energy Q – heat supplied to the system W – work done on the system [1] equation [1] correct definition