In a gravity free space, a man of mass M standing at a height h above the floor, throws a ball of mass m straight down with a speed u. When the ball reaches the floor, the distance of the man above the floor will be

Explanation

When the man throws the ball with velocity u, he recoils with velocity V.
mu = MV
`V=(mu)/(M)`
time taken by the ball to reach the ground `t=(h)/(u)` Distance moved by man in this time
`t=v.t=("mu")/(M).(h)/(u)=(m)/(M).h`
Height of man at the time the ball strikes the ground is `H=h+(m)/(M)h " " H=h(1+(m)/(M))`.