9814 H3 Physics - HCI 2024 Complete H3 Topical Examples and Tutorial Solutions

Hwa Chong Institution (College) MOE H3 Physics 2024 A1. Inertial Frames of Reference 1 Suggested Solutions for Worked Examples 1 a) Car,Truck Car,Earth Earth,Truck -1 Car,Truck 25 30 5 m s V V V V =+ = − =− The observer in the truck observes that the car moves in the opposite direction at a constant speed of 5 m s-1. b) Truck,Car Truck,Earth Earth,Car -1 Truck,Car 30 25 5 m s V V V V =+ = − =+ The observer in the car observes that the truck moves in the forward direction at a constant speed of 5 m s-1. c) Car,Truck Car,Truck ( 5)(60) 300 md V t = = − =− 2 spider,Earth spider,passenger passenger,tr ain train,Earth -1 spider,Earth 0.5 1.2 3.1 3.8 m s V V V V V = + + =− + + = 3 a) Yes. In both Earth and reference frame M, the speeds of the carts are constant. Hence, their kinetic energies are constant. b) No net external force acting on the system. Hence, no change in momentum and energy. Therefore, the isolated system containing only cart 1 is closed. c) No net external force acting on the system. Hence, no change in momentum and energy. Therefore, the isolated system containing only cart 2 is closed. 4 a) Merry-go-round: Its velocity changes, there is an acceleration towards the centre of the circle. It is a non-inertial reference frame. b) Airplane taking off: The velocity must increase. There is an acceleration associated with it. It is a non-inertial reference frame. c) Train at constant speed: The velocity is constant and no acceleration. It is an inertial frame of reference.

Hwa Chong Institution (College) MOE H3 Physics 2024 A1. Inertial Frames of Reference 2 5 a) Head-on collision in the Earth frame, By RSOA = RSOS, 2 1 1 2 1 2 1 20.80 0 0.80 u u v v v v v v − = − − = − → = + By PCOLM, 12 22 -1 2 -1 1 (0.36)(0) (0.12)(0.80) (0.36) (0.12) (0.12)(0.80) (0.36)(0.80 ) (0.12) 0.40 m s (moves rightwards) 0.40 m s (moves leftwards) vv vv v v + = + = + + =− = The relative velocity is 0.80 m s-1. -1 1 1 1 -1 2 2 2 0.40 0 0.40 m s (leftwards) 0.40 ( 0.80) 1.20 m s (rightwards) V v u V v u  = − = − =  = − =− − + =− b) -1 1 1 1 -1 2 2 2 (0.36)(0.40) 0.144 kg m s (leftwards) (0.12)( 1.20) 0.144 kg m s (rightwards) p m V p m V  =  = =  =  = − =− Please note that the total change in momentum in the cart 1 and 2 system is zero. This indicates that there is no net external force acting on the system. c) 22 ,1 22 ,2 1 (0.36)(0.40 0 ) 0.0288 J2 1(0.12)(( 0.40) 0.80 ) 0.0288 J2 k k E E  = − =  = − − =− Please note that the total change in the kinetic energy of the system is zero. This indicates that there is no energy lost in this elastic collision. d) Reference frame M moves at a constant speed of 0.20 m s -1 towards right (towards cart 2) -1 1 , 1 , , -1 2, 2, , 0 0.20 0.20 m s (leftwards) 0.80 0.20 1.00 m s (leftwards) M Earth Earth M M Earth Earth M u u u u u u = + = + = = + = + = In reference frame M,