Given that, the ball collides elastic, \(\Rightarrow\) velaity initial = velocity final
From fig,
\(V_i=V \cos 60^{\circ}(-\hat{j})\)
\(V_f=V \cos 60(-\hat{j})\)
Change in momentum \(=m\left(\vec{V}_f-\vec{V}_i\right)\)
\(=m\left(-V \cos 60^{\circ}+V \cos 68^{\circ}\right)\)
\(=m(0)\)
\(=0\)
$\left(g=10\, m s^{-2}\right)$