Question 81421
the object "hits the ground" when it is at height 0 ... so set h=0 and solve for t


{{{0=-16t^2+90t+3}}} ... using quadratic formula {{{t=(-90 +- sqrt(90^2-4*(-16)*3))/(2*(-16))}}} ... {{{t=(-90 +- sqrt(8292))/(-32)}}}


so t=-0.033 and t=5.658 ... the negative value is unrealistic