The height above ground level in metres of a missile lanunched vertically, is given by h(t)=-16t^3+100t. at what time is the missile 50m above the ground level? [t is time in seconds]

Answer 1

just solve
-16t^3+100t = 50
in the usual way

Although, I think you want the height in feet, since in metric units, g/2 = -4.9, not -16

Answer 2

Result