In a free space a rifle on mass `M` shoots a bullet of mass `m` at a stationary block of mass `M` distance `D` away from it . When the bullet has moved through a distance `d` towards the block the centre of mass of the bullet `-` block system is at a distance of `:`

Options

A. `((D-d)m)/(M+m)` from the block
B. `(md+MD)/(M+m)` from the rifle
C. `(2dm+DM)/(M+m)` from the rifle
D. `(D-d)(M)/(M+m)` from the bullet

Answer

A, B, D

Explanation

As, `Mx=m(D-d-x)`
`x=(m(D-d))/(M+m)` from the block
and `x'=D-d-x`
`=((D-d)M)/(M+m)` from the bullet.