There object `A ,B` and `C` are kept is a straing line a frictionless horizontal surface . These have masses have increase on `2m` and `m` respectively . The object `A` move toward `B` with a speed `9` m//s and makes as elastic collision with a there after `B` makes completely inclesis with `C` . All motion over on the same straight line . Find the first speed of the object `C`

Answer

4

Explanation

After the first collision,
`m v_A = m v_A^' + 2 mv_B^'`
`1 = (v_B^' - v_A^')/(v_A) implies v_B^' = 6m//s`
After the second collision,
`2m v_B^' = (2m + m) v_c implies v_C = (2//3) v_B^' implies v_C = 4m//s`