A man is standing on top of a building 100 m high. He throws two vertically, one at t = 0 and other after a time interval (less than 2 seconds). The later ball is thrown at a velocity of half the first. The vertical gap between first and second ball is +15 m at t = 2 . The gap is found to remain constant. Calculate the velocity with which the * were thrown and the exact time interval between their throw.
