A small block of mass 'm' is placed on bigger block of mass `M_(1)` which is placed on a fractionless horizontal surface. The two blocks are given equal speed `u_(1)` but opposite directions, as shown in the figure. After sometime, it is observed that both blocks are moving in the direction of motion of the lower block, with a speed greater than `(u)/(2)`. It can be concluded that -

Options

A. `M gt 3m`
B. `3M lt m`
C. `m gt 2M`
D. M,m can have any value such that `M gt m`

Answer

A

Explanation

Conserving linear momentum in horizontal direction w.r.t ground
`Mu - mu= (M+m)v`
It `v gt (u)/(2) rArr ((M-m))/((M+m))u gt (u)/(2)`
`rArr ((M-m))/((M+m))gt (1)/(2), rArr M gt 3m`