Two particles start simultaneously from the same point and move along two straight lines, one with uniform velocity $\overrightarrow{\mathrm{u}}$ and the other from rest with uniform acceleration $\overrightarrow{\mathrm{f}}$. Let $\alpha$ be the angle between their directions of motion. The relative velocity of the second particle w.r.t. the first is least after a time.\\
(1) $\frac{u\cos\alpha}{f}$\\
(2) $\frac{u\sin\alpha}{f}$\\
(3) $\frac{f\cos\alpha}{u}$\\
(4) $u\sin\alpha$