Question

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

Answer 1

Correct Answer - 3 kg m `s^(-1)`
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 `m s^(-1) `.