posted by sara .
A ball is thrown horizontally with an initial velocity of 20.0 m/s from the edge of a building of a certain height. The ball lands at a horizontal distance of 82.0 m from the base of the building. What is the height of the building?
time, t=82/20=4.05 s
u=initial vertical velocity = 0 m/s
Can you take it from here?