A particle is projected from a point O with velocity u at an angle of 60∘ with the horizontal. When it is moving in a direction at right angles to its direction at O, its velocity then is given by:
Solutions · 1
Official solution
The horizontal component of velocity is conserved. At the new instant the velocity v makes angle 30∘ with the horizontal (perpendicular to the original 60∘ direction):
\[u\cos60^{\circ}=v\cos30^{\circ} \implies \frac u2=v\cdot\frac{\sqrt{3}}2 \implies v=\frac u{\sqrt{3}}\]