Question

A body of mass 4m is lying in x-y plane at rest

Answer 1

From the law of conservation of momentum,Magnitude of the momentum of heavier piece of mass 2m =        Magnitude of the vector sum of moemntum of each peice of mass m
(2m)v'=underroot (mv)sq+(mv)sq
=2√mv(2)v'
=2√vv'=underroot vsq.
KE generated:
KE =1/2mvsq.+1/2mvsq.+1/2(2m)(v')sq.   
=1/2(mvsq.+mvsq.+(2m)(vsq./2))       
 =1/2(3mvsq)