An object is projected vertically upwwards at 8 meters per second from the roof of a building which is 60 meters high.it strikes the balcony below in 4 seconds.What is the velocity at which the object strikes the balcony?

Answer 1

The building height doesn't matter.
On its way down, as the thrown object passes the roof, its speed will again be 8 m/s, but DOWN. Since the object was thrown, the elapsed time is then (2*Vo)/g = 1.663 s. It will spend the remaining
t' = 4 - 1.663 = 2.406 seconds
falling to the balcony. Its velocity will then be 8.0 + gt' = 31.6 m/s