From the top of a tower of height 200 m, a ball A is projected up with 10 ms-1, and 2s later another ball B is projected vertically down with the same speed. Then

Ball A will return to the top of tower after T=2ug=2×1010=2s with speed of 10 ms-1 downward. And this time, B is also projected downwards with 10 ms-1. So both reach ground simultaneously. Also they will hit the ground with the same speed.