The velocity of a projectile at the initial point $$A$$ is $$\left( {2\hat i + 3\hat j} \right)m/s.$$    Its velocity (in $$m/s$$ ) at point $$B$$ is

Solution :
Concept
As we know that in projectile motion only velocity of $$y$$ component change, whereas velocity of $$x$$ component remains constant.
From the figure, the $$x$$-component remains unchanged, while the $$y$$-component is reversed. Thus, the velocity at point $$B$$ is $$\left( {2\hat i - 3\hat j} \right)m{s^{ - 1}}.$$