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Work, Energy and Power
Question
Wired Faculty App

When a ball of mass m moving with velocity u collides elastically with a wall normally, then what is the change in momentum of the ball?

Answer

Initial velocity of the ball =u 
Mass of the ball = m 
So, initial momentum of the ball = m u 
After collision, the ball changes it's direction. 
Therefore, momentum = - mu 
Therefore, 
Change in momentum of the ball = mu - (- mu) = 2mu.

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