Question

A particle projected at some angle with velocity $50m/s$, crosses a $20m$ high wall, after $4s$ from the time of projection. The angle of projection of the particle is ?

• A. ${30}^o$
• B. ${45}^o$
• C. ${60}^o$
• D. ${53}^o$

Answer 1

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

If angle of projection be $\theta$ then initial vertical velocity will be $50Sin\theta$

so after $4s$ its height will be $h=50Sin\theta \left(4\right)-\frac{g(4{)}^2}{2}$

Putting $g=10m/s^2$ and $h=20m$ we get $Sin\theta =\frac{1}{2}$

so $\theta ={30}^0$