A hockey ball of mass 200 g travelling at 10 m s-1 is struck by a 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 ms^-1

Hence, the change in momentum of the hockey ball is 3 kg ms^-1 .