A hockey ball of mass 200 g travelling at 10 m s–1 is struck bya hockey stick so as to return it along its original path with a velocity at 5 m s–1. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.

Mass of the hockey ball, m= 200 g = 0.2 kg
Hockey ball travels with velocity, v₁= 10 m/s
Initial momentum = mv₁
Hockey ball travels in the opposite direction with velocity, v₂= -5 m/s
Final momentum = mv₂
Change in momentum = mv₁- mv₂= 0.2 [10 – (-5)] = 0.2 (15) = 3 kg m s⁻¹
Hence, the change in momentum of the hockey ball is 3 kg m s⁻¹.

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