Question

A stone is projected 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 $(g=10m/{sec}^2)$

• A. ${30}^0$
• B. ${45}^0$
• C. ${50.2}^0$
• D. ${60}^0$

Answer 1

The correct option is A ${30}^0$

Let angle of projection is $\theta$ then we have

$U_x$= 25cos$\theta$

$U_y$= 25sin$\theta$

after 2 sec it clears a wall of 5m height that means its height from ground is nearly 5m

H = $U_{y}t$ - $g{t}^2$/2

5 = 25sin$\theta$× 2 - 10×4/2

5 + 20 = 50sin$\theta$

sin$\theta$ = 1/2 or $\theta$= ${30}^o$