Three objects `A` ,` B` and `C` are kept in a straight line on a smooth horizontal surface. These have masses `m `, `2m` and `3 m` , respectively . The head - on elastic collision takes place between `A` and `B` and then `B` makes completely inelastic collision with `C`. All motions occur on the same straight line. The final speed of `C` will be

Answer

`4 m//s`

Explanation

For collision between A & B
`v_(A) = ((m - 2m))/((m + 2m)) (9) = -3 ms^(-1)`
`v_(B) = (2(m))/((m + 2m))(9) = +6ms^(-1)`
For collision between B and C
`v_(c ) = ((2m)/(2m + m)) (6) = 4ms^(-1)`