Two particles of a mass 2m and m are tied with an inextensible string the particle of mass m is given a speed V as shown in the figure. Find the speed with which the particle of mass 2m starts moving.

Explanation

A string will appy equal force at its both ends and hence equal impluses. Thus, for particle of mass 2m.
`I=2mv_(1)" "…(i)`
For particle of mass m,
`I=mv-mv_(1)" "…(ii)`
Solving equation (i) and (ii)
`mv-mv_(1)=2mv_(1)`
`v_(1)=(mv)/(3m)=v/3`