Question

A rock is thrown upward from level ground in such a way that the maximum height of its flight is equal to its horizontal range R. At what angle u is the rock thrown?

Answer 1

considering the rock; $d=y_{max}$

$\frac{v^2sin2\theta}{g}=\frac{v^2sin^2\theta}{2g}$

$2sin\theta cos\theta=\frac{sin^2\theta}{2}$

$2cos\theta=\frac{sin\theta}{2}$

$tan\theta=4$

$\theta=tan^{-1}4=75.96^0$