Question

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

Answer 1

$\bf{\underline{\underline{Answer:}}}$

$\bf{\therefore\:3\:kg\:m\:{s}^{-1}}$

$\bf{\underline{Given:}}$

$⟹ {Mass \:of\: hockey\: ball, \:m=200\:g\:=200/1000\:kg\:=\:0.2\:kg}$

$⟹{Initial \:velocity\: of\: hockey\: ball,\: u = 10\: m\: {s}^{-1}}$

$⟹ {Final \:velocity\: of\: hockey \:ball, v = - 5 m {s}^{-1}}$ (because direction becomes opposite)

$\bf{\underline {To\:Find:}}$

$⟹ {Change \:in \:momentum\: =\:?}$

$\bf{\underline{\underline{Step\: by\: step \:explanation:}}}$

We know that,

Momentum = Mass × Velocity

Therefore , momentum of ball before getting struck

$⟹ {0.2\:×\:10\: = \:2 \:kg\: m \:{s}^{-1}}$

Momentum of ball after getting struck

$⟹ {0.2\:×\:-5 \:= \:- 1\:kg\: m\: {s}^{-1}}$

Therefore, Change in momentum

= Momentum before getting struck - Momentum after getting struck

$={2\:-\:(-1)}$

$⟹ { 2 \:+\: 1\: = \:3\: kg \:m\: {s}^{-1}}$

Thus, change in momentum of ball after getting stuck is $\bf{3\:kg\:m\:{s}^{-1}}$