Question

A football is kicked at ground level with a speed of 18.0 m/s at an angle of 35.0 degrees to the horizontal. How much later does it hit the ground?

Answer 1

object will hit the ground after twice the time of reaching max height(symmetry of problem)
the time that it takes to reach max height could be evaluate from the equation:
\[v=v_\sin 35^0 - g t\] where v is vertical component of velocity. We know that this velocity is zero when it reaches max height(moment of changing direction of vertical component) so
\[0=vsin 35-g t \rightarrow t=\frac{ vsin35^o }{g }\]

Answer 2

twice that time will be 2,1 s