science
posted by peter .
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?

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