- Home
- Standard 9
- Science
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 magnitude of change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.
$6$ $kg\, m\, s^{-1}$
$3$ $kg\, m\, s^{-1}$
$2$ $kg\, m\, s^{-1}$
$4$ $kg\, m\, s^{-1}$
Solution
Mass of the hockey ball, $m= 200\, g = 0.2\, kg$
Hockey ball travels with velocity, $v_1= 10 \,m/s$
Initial momentum $= mv_1$
Hockey ball travels in the opposite direction with velocity,$ v_2= -5 \,m/s$
Final momentum $= mv_2$
Change in momentum $= mv_1- mv_2= 0.2 [10 – (-5)] = 0.2 (15) = 3 \,kg \,m\, s^{-1}$
Hence, the change in momentum of the hockey ball is $3$ $kg\, m\, s^{-1}.$
