A rock is thrown downward from a platform that is 172 feet above ground at 30 feet per second.  Use the projectile formula -16t^2+v0t+h0 determine when the rock hit the ground.   [Recall that v0 is the initial velocity of the object and h0  is the initial height of the object.] Answer:  The rock will hit the ground after _______?______ and (select the answer)--->(feet,feet per second,seconds, none of these units)

A rock is thrown downward from a platform that is 172 feet above ground at 30 feet per second.  Use the projectile formula -16t^2+v0t+h0 determine when the rock hit the ground.  

[Recall that v0 is the initial velocity of the object and h0  is the initial height of the object.]

Answer:  The rock will hit the ground after _______?______ and (select the answer)--->(feet,feet per second,seconds, none of these units)