Question

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

Answer 1

HELLO DEAR,

GIVEN:-

Mass of ball (m) = 200 g = 0.2 kg

Initial velocity of ball (${u_1}$) = 10 m ${s^{-1}}$

Initial momentum of ball = ${mu_1}$ = 0.2 kg x 10 m${s^{-1}}$ = 2 N s

Final velocity of ball ${(u_2)}$ = - 5 m ${s^{-1}}$ (Minus sign denotes that ball is moving in opposite direction.)

Final momentum of ball =${mu_2}$ = 0.2 kg x -5 m${s^{-1}}$ = -1 N s

Change in momentum = Final momentum - Initial momentum = - 1Ns - 2Ns = - 3N s. (Minus sign denotes change in momentum in the direction opposite to the direction of initial momentum of the ball.

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Answer 2

Let the initial momentum = mu = 0.2 *10 = 2kg m/s

and final momentum = mv = 0.2*(-5) = -1kg m/s (because opposite direction)

hence change in momentum = m(v-u)

= (-1-2)

= -3kg m/s