Mass of the hockey ball, *m*= 200 g = 0.2 kg

Hockey ball travels with velocity, *v*_{1}= 10 m/s

Initial momentum = *mv*_{1}

Hockey ball travels in the opposite direction with velocity, *v*_{2}= -5 m/s

Final momentum = *mv*_{2}

Change in momentum = *mv*_{1}– *mv*_{2}= 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} .