Question

A man of `50 kg` mass is standing in a gravity free space at a height of `10m` above the floor. He throws a stone of `0.5 kg` mass downwards with a speed `2m//s`. When the stone reaches the floor, the distance of the man above the floor will be
A. `9.9 m`
B. `10.1 m`
C. `1.0 m`
D. `20 m`

Answer 1

Correct Answer - B
Here, `m_(1)=50 kg, m_(2)=0.5kg`
`u_(1)=?,u_(2)=2m//s`
By momentum conservation,
`m_(1)u_(1)+m_(2)u_(2)=0`
`=u_(1)=(-m_(2)u_(2))/(m_(1))=(-0.5xx2)/(50)=(1)/(50)m//s`
Negative sign is for upward motion of man. In gravity free space, time taken by stone to reach the floor, `t=(s)/(m_(1))=(10)/(2)=5s`
Upward distance moved by the man `=u_(1)xxt`
`=(1)/(50)xx5=0.1m.`
`:.` Distance of man above the floor
`=(10+0.1)m=10.1m`