A particle is projected from a point $\mathrm{O}$ with velocity $u$ at an angle of $60^{\circ}$ with the horizontal. When it is moving in a direction at right angles to its direction at $O$, its velocity then is given by

• A

  $\frac{u}{3}$
• B

  $\frac{\mathrm{u}}{2}$
• C

  $\frac{2 u}{3}$
• Correct answer
  D

  $\frac{\mathrm{u}}{\sqrt{3}}$

Solution

$\mathrm{u} \cos 60^{\circ}=\mathrm{v} \cos 30^{\circ}$ $$ v=\frac{4}{\sqrt{3}} $$

Hence, the correct answer is option: 'D'.