A shell at rest on a smooth horizontal surface explodes into two fragments of masses m1 and m2. If just after explosion m1 move with speed u, then work done by internal forces during explosion is
No external force is acting on the shell
So momentum will be conserved
Using momentum conservation, m1u=m2v----------(1)
Now using work energy theorem,
W=m1u22+m2v22
From equation 1
W=m1u22(m1+m2m2)
Hence work done is 12m1u2(1+m1m2)