^Explosion of a bomb
Before explosion, suppose the bomb is at rest i.e., initial total momentum is zero. Now when it explodes, it breaks up into several pieces of masses m1, m2, m3, etc., which fly off in different directions with velocities etc. in such a manner that vector sum of linear momentum of all the parts after explosion is zero or the linear momentum of any piece is nullified by the resultant of the linear momenta of the remaining. During explosions total energy is always conserved however KE after explosion increase. This is possible because the chemical energy of the explosive is converted into KE. Thus we can say that the internal forces acting on a system can never change the linear momentum of a system but can change the KE of the system.