A hang glider pilot accidentally drops her compass from the top of a 400-foot cliff. The height h of the compass after t seconds is given by the quadratic equation h=−16t^2+400. When will the compass hit the ground?

The compass will hit the ground when h = 0.

Substituting h = 0 into the equation, we get:
0 = -16t^2 + 400
16t^2 = 400
t^2 = 25
t = √25
t = 5 seconds