Question

A stone is projected from the ground with velocity 25 m/s . Two seconds later, it just clears a wall 5 m high. The angle of projection of the stone is (g=10 m/$s^2$)

• A. ${30}^{\circ }$
• B. ${45}^{\circ }$
• C. ${50.2}^{\circ }$
• D. ${60}^{\circ }$

Answer 1

The correct option is A ${30}^{\circ }$

For vertical uopward motion h = ut - $\frac{1}{2}$g $t^2$
5 = (25 sin $\theta$) $\times$ 2 - $\frac{1}{2}$ $\times$ 10 $\times$ ${\left(2\right)}^2$
$\Rightarrow$ 25 = 50 sin $\theta$ $\Rightarrow$ sin $\theta$ = $\frac{1}{2}$ $\Rightarrow$ $\theta$ = ${30}^{\circ }$