How long untile projectile hits ground?

Question

A projectile is shot vertically from ground level. Its height, in feet, after t seconds is given by h=88t-16t². How long will it take the projectile to hit the ground?

Answer 1

First find the velocity function which in this case is v(t) = 88 - 32t. The velocity goes to 0 at the peak of the trajectory so 32t= 88 and t at the highest point is 275 sec. The projectile will strike the ground at 2t which is

5.5sec.