Let V1 and V2 be the velocities of blocks A and B immediately after the elastic collision: v1 = (
m1−m2
m1+m2
)m = (
m−2m
m+2m
)×9 = - 3 m/s v2 = (
2m1
m1+m2
)m = (
3m
m+2m
)×9 = 6 m/s
After the perfectly inelastic collision between blocks B and C, let v be the common velocity. Applying centre of mass concept, we get 2mv2 = (2m + m) v ⇒ v =