A bullet of mass m moving with velocity v strikes a block of mass Mat rest and gets embedded into it. The kinetic energy of the composite block will be

According to law of consecrations of momentummv=(m+M)v′  where v′= velocity of composite block  ∴ V′=mM+mV  K.E. of composite block =12(M+m)v′2 ∴  K.E. =12(M+m)mM+m2v2 =12mv2mM+m