A ball is thrown off a cliff from a ht of 180 ft above sea level. The ht s of the ball above sea water level at time t is s(t)=-16t2+32t+180. When will the ball strike the water?
When the ball strikes the water, the ht above water will be 0.
h = -16t^2 +32t + 180 = 0,
Solve for t using the Quadratic Formula
and get:
t = -2.5, and 4.5s.
Select the positive value t:
t = 4.5s.