Question

Two second after projection a projectile is travelling in a direction inclined at $30^{\circ }$ with horizontal, after one more second it is travelling horizontally. Angle of projection (in degree) with horizontal divided by $10$ is [Take $g=10m{s}^{-2}$ ]

Answer 1

Answer: 6

Let angle made by $\vec{v}$ initially and after time $t$ be $\theta$ and $\alpha$ respectively.
$\tan 30^{\circ }=\frac{u\sin \theta -g\times 2}{u\cos \theta }$ ......(i)
$\tan 0^{\circ }=\frac{u\sin \theta -g\times 3}{u\cos \theta }$ ..... (ii)
$\therefore \theta =60^{\circ }$