NEET (UG) 2023 — Question 19

The player initially moves south with velocity $\vec{v}_i = -u \hat{j}$. After turning east, the final velocity is $\vec{v}_f = u \hat{i}$. Change in momentum: $\Delta \vec{p} = m\vec{v}_f - m\vec{v}_i = m u \hat{i} - m u (-\hat{j}) = m u (\hat{i} + \hat{j})$. The direction of $\Delta \vec{p}$ is north-east (since $\hat{i}+\hat{j}$ points at 45° between east and north). Force $\vec{F} = \frac{\Delta \vec{p}}{\Delta t}$, so the force acts in the same direction as $\Delta \vec{p}$. Thus the force on the player while turning is along north-east.