Question 13

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.

Answer

Mass of the hockey ball, *m* = 200 g = 200 / 1000 = 0.2 kg

Initial velocity, *v _{1}* = 10 m/s

Initial momentum = *mv _{1}*

Final velocity, *v _{2}* = −5 m/s

Final momentum = *mv _{2}*

Change in momentum = *mv _{1} − mv_{2} = m(v_{1} - v_{2})*

= 0.2 [10 − (−5)] = 0.2 (15) = 3.0 kg m/s

Hence, the change in momentum of the hockey ball is 3 kg m/s.

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- NCERT Chapter