Physics
posted by Ashley .
A ball is thrown horizontally from the top of a building 55.4 m high. The ball strikes the ground at a point 65 m from the base of the building.
The acceleration of gravity is 9.8 m/s2 .
Find the time the ball is in motion in seconds.

hf=hi+vi*t4.9t^2
solve for time. 
how do i solve for time when i don't know initial velocity?

dy(height)=1/2 times acceleration due to gravity(9.81) times time squared