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