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06/01/2021 12:48 pm
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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.
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06/01/2021 12:53 pm
Mass of ball(m) = 200g = 0.2 kg
Initial velocity of ball (u1) = 10 ms-1
∴ Initial momentum of ball = mu1
= 0.2 kg x 10ms-1 = 2 Ns
Final velocity of ball(u2) = -5 ms-1
(Minus sign denotes that ball is moving in opposite direction.)
∴ Final momentum of ball = mu2
= 0.2 kg x -5 ms-1 = -1 Ns
∴ Change in momentum
= Final momentum - Initial momentum
= -1 N s - 2 N = -3 Ns
Minus sign denotes that change in momentum is in the direction opposite to the direction of initial momentum of the ball.