(DHS) 2024 Prelim Phy P1 Ans_final

1 2024 DHS H2 Physics Prelim Paper 1 Suggested Solutions Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 A A B D B A C B C D Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 Q19 Q20 C C C D C D A C A C Q21 Q22 Q23 Q24 Q25 Q26 Q27 Q28 Q29 Q30 A D A B C D D B B A 1 A By dimensional analysis, Units of √𝑔𝜆 = √m2 s−2 = m s−1 2 A s2 = s – s1 By Pythagoras theorem, s2 = √1402 + 1502 = 205 cm tan  = 150 140 or  = 47o Hence  = −17o anti-clockwise with respect to positive x-axis 3 B a = (v – u)/t = (0 -15)/1.2 = -12.5 m s-2 v2 = u2 + 2as 02 = 152 + 2(-12.5)s s = 9.0 m Closest distance = 9.0 + 15(0.10) = 10.5 m x 1200 s1 =150 cm s =140 cm −s1 =150 cm 30o s2 

2 4 D For a (perfectly) elastic collision between two bodies, the relative speed of approach is equal to the relative speed of separation. relative speed of P approaching Q Option relative speed of Q separating from P equal ? ( ) ( ) − −− = 1 1.30 0.50 1.80 m s A ( ) ( ) 10.58 0.22 0.36 m s −−=  B ( ) ( ) 10.40 0.40 0.00 m s −−=  C ( ) ( ) 10.99 0.19 1.18 m s −− − =  D ( ) ( ) 11.30 0.50 1.80 m s −− − =  5 B By Newton’s Third Law of Motion, the magnitude of the force exerted on m1 by m2 is equal to the magnitude of the force exerted on m2 by m1. 6 A Air resistance increases proportionately with speed. Resultant force = Weight – Air resistance 7 C Work done by a constant force on an object is defined as the product of the force and its displacement in the direction of the force. 8 B (0.5 x power output/power input) = 0.80 (0.5 x 200 000 x 250/power input) = 0.80 Power input = 31.3 MW 9 C Period, 𝑇 = 60 𝑥 60 s 𝜔 = 2𝜋 𝑇 = 2𝜋 60 × 60 = 1.75 × 10−3 rad s−1 10 D At the Earth’s surface: 2 GMmW R= At orbit: 22 1 49 49( 6 ) GMm GMm WF R R R = = = + 

3 11 C For geostationary satellites, all satellites orbit the Earth at a fixed distance from the Earth, r, and the orbital period T is the same as Earth’s rotation of 24 hours. Hence, all geostationary satellites also have the same angular velocity by 2 T  = (options A and D are eliminated) For a satellite, the gravitational force FG provides the centripetal force. Therefore, 2 2 2 2 GMm mrr GM rgr   = == Therefore, the centripetal acceleration which is dependent on the radius and orbital period is the same for geostationary satellites. (Option B is eliminated) Even though the speed of the satellites are the same, as given by the equation vr = , the mass of the satellites may be different. So by 21 2KE mv= , the kinetic energy of the satellites may be different. (Option C is the answer) 12 C Since the mixture is in thermal equilibrium, gases X and Y have the same temperature. Since avgT KE , the average kinetic energy of gases X and Y are the same. Therefore, the average kinetic energy of molecules of X is 6.0 × 10-21 J. 13 C Let Q be the heat supplied to the liquid per minute, Conside