An airplane is moving with velocity `v_0` horizontally at a height h. If a projectile is fired at the instant when the plane is overhead, what must be the angle of projection and minimum velocity of projection in order that it may hit the airplane ?

Answer

`u_("min")=sqrt(v_0^2+2gh)` and `alpha=cos^(-1) v_0/(sqrt(v_0^2+2gh))`