A rock is dropped from bridge over a river 180 feet above the water.

Answer 1

h(t) = -16t^2 + 180

the rock hits the water when

h(t) = 0 = -16t^2 + 180

16t^2 = 180

t^2 = 180/16

t= sqr(180/16) = about 3.35 seconds to hit the water