(main)[5]
A particle $P$ is projected from a point $O$ on horizontal ground with speed $V\,\text{m s}^{-1}$ at an angle of $\theta^\circ$ above the horizontal. $4\,\text{s}$ after projection, the particle is at point $A$, where $OA = 40\,\text{m}$ and the line $OA$ is inclined at $30^\circ$ to the horizontal. Calculate $V$ and $\theta$.