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.
Class 9 - Science - Force and Laws of Motion Page 129
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Given,
Mass of hockey ball, m = 200 g = 200/1000 kg = 0.2 kg
Initial velocity of hockey ball, u = 10 m/s
Final velocity of hockey ball, v = – 5 m/s (because direction becomes opposite)
Change in momentum =?
We know that,
Momentum = mass x velocity
Therefore, Momentum of ball before getting struck = 0.2 kg x 10 m/s = 2 kg m/s
Momentum of ball after getting struck = 0.2 kg x - 5m/s = – 1 kg m/s
Therefore, change in momentum = momentum before getting struck – momentum after getting struck
= 2 kg m/s – (–1 kg m/s)
= 2 kg m/s + 1 kg m/s = 3 kg m/s
Thus, change of momentum of ball after getting struck = 3 kg m/s
Mass of hockey ball, m = 200 g = 200/1000 kg = 0.2 kg
Initial velocity of hockey ball, u = 10 m/s
Final velocity of hockey ball, v = – 5 m/s (because direction becomes opposite)
Change in momentum =?
We know that,
Momentum = mass x velocity
Therefore, Momentum of ball before getting struck = 0.2 kg x 10 m/s = 2 kg m/s
Momentum of ball after getting struck = 0.2 kg x - 5m/s = – 1 kg m/s
Therefore, change in momentum = momentum before getting struck – momentum after getting struck
= 2 kg m/s – (–1 kg m/s)
= 2 kg m/s + 1 kg m/s = 3 kg m/s
Thus, change of momentum of ball after getting struck = 3 kg m/s
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