DHS 2023 JC1 Promos Physics (Solutions)

DUNMAN HIGH SCHOOL 2023 PHYSICS H2 (YEAR 5) 1 Answers to Promotional Exam Section A 1 2 3 4 5 6 7 8 9 10 A B C B C C D D A D 11 12 13 14 15 A D B C B 1 A Energy produced = Pt = 3.0 x 109 x 2.0 x 10-12 = 6.0 x 10-3 J = 6.0 x 10-15 TJ 2 B Recall: v = vf - vi The horizontal component of vi = vf since there’s no horizontal acceleration, so v is vertical. v = 12 sin 25o = 5.1 m s-1 3 C Using: 21s 2ut at=+ On Moon: ( ) 2 moon 131 2 at= −−− On Earth: ( ) ( ) 2 moon Earth 12 6 22 at= −−− 25o vf −vi = 12 m s−1 v Solving (1) and (2), 2 moon Earth 2 moon Earth 62 3 3 at a t tt =  =

DUNMAN HIGH SCHOOL 2023 PHYSICS H2 (YEAR 5) 2 4 B Before time instant B, the cars move towards each other. After time instant B, the cars move away from each other. 5 C The acceleration of the system can be found by mtotala = 12. ∴ a = 2.0 m s−1 Considering the forces acting on the 1.0 kg mass, 2 on 1 1 2 on 1 12 12 1.0(2.0) 10 N N m a N −= =− = Considering the forces acting on the 3.0 kg mass, 2 on 3 3 3.0(2.0) 6.0 N N m a= = = 6 C At equilibrium, the 3 forces on the object formed a closed triangle. By Pythagoras theorem, √F1 2 +F2 2 = 100. That would rule out A and B. Since the net force on the object is zero, then horizontally, F1 cos a = F2 cos b Since b > a, cos b < cos a, so F2 > F1 1.0 kg 2.0 kg 3.0 kg 12 N F1 F2 W a b N2 on 1 N2 on 3

DUNMAN HIGH SCHOOL 2023 PHYSICS H2 (YEAR 5) 3 7 D Fully submerged: Ufull = Vdisp waterwaterg = Vicewaterg Floating (at equilibrium) Ufloat = Wice = miceg = Viceiceg Hence upthrust when fully submerged upthrust when floating = water ice = 1.1 8 D D = kv2 where k is a constant of proportionality At 12 m s-1, the driving force provided by the 2 engines is equal and opposite to the total drag. 3 3 36000 2 (12) 720000 (12) P Dv k k = = = If only 1 engine is on, the new maximum speed v’ can be found by: 3 3 33 3 1 720000360000 ( ') (12) 360000' (12 )720000 12 2 9.5 m s v v − = = = = 9 A Since they are rotating together with the horizontal turntable without slipping, the angular velocity of the two coins is the same as that of the horizontal turntable, 12 1 2 1    = = 11 22 1 2 vr vr r r  = =

DUNMAN HIGH SCHOOL 2023 PHYSICS H2 (YEAR 5) 4 10 D Consider forces acting on man of mass m when in orbit, W – N = mv2 r (1) Since the spac