The velocity of a projectile at the initial point A is $(2\hat{\mathbf{i}}+3\hat{\mathbf{j}})$ ms^-1. Its velocity (in ms^-1) at point B is          

From the question's figure, the x-component remain unchanged, while the y-component is reversed. Then, the velocity at point B is ($2\hat{\mathbf{i}}-3\hat{\mathbf{j}}$) ms^-1.