How does Newton's third law apply on explosion of a bomb?

I have read that when a bomb explodes into fragments, then total momentum of the system remains conserved. And law of conservation of momentum is based on newton's second and third law. So I am not able to understand or get an intuition of how Newton's third law applies on explosion.

4 Answers 4

Simply stated, Newton’s third law says for every force there is an equal and opposite force. From this we can say that, in the case of an exploding part, each fragment of the part exerts an equal and opposite force on the other fragment causing them to separate with equal and opposite momenta. The source of the forces are the rapid release of heat and large quantities of high pressure gases. An example is the explosion propelling a bullet giving it momentum in one direction and the recoil force of the bullet on the gun giving the gun equal momentum in the opposite direction.

You can also think of the original part prior to the explosion as consisting of two parts. Attached to part 1 is a compressed massless ideal spring (mechanical potential energy equivalent of the chemical potential energy of the explosive) and part 2 is in contact with the other end of the spring.

The spring is tripped (explosive ignited) so that part 1 propels part 2 with a force in one direction. Per Newton’s third law, part 2 applies an equal and opposite force on part 1 propelling it in the opposite direction. Since, per Newton’s second law, the force on an object equals its change in momentum, each part undergoes an equal and opposite change in momentum.