# Disintegration of Particles

1. Feb 15, 2008

### lugita15

Consider a particle at rest (what I mean is that the particle has no velocity, but also has no force acting on it) that spontaneously disintegrates into more than one particle, e.g. two or three particles. Before the particle disintegrates, there is no kinetic energy in the system. Afterwards, there is kinetic energy.

How do you reconcile this with the Law of Conservation of Energy? Do you assume that the initial particle has some potential energy associated with it? The existence of potential energy implies the presence of a conservative force. But if there were some kind of force acting on the particle, this would contradict the assumption that the particle had no forces acting on it to begin with.

In special relativity, this problem doesn't arise because every particle has a rest energy, $$m_{0}c^{2}.$$ But what about in classical mechanics? Before Einstein came out with the theory of relativity, was the phenomenon of a particle splitting up into more than one particles a completely unexplainable mystery?

Any help would be greatly appreciated.

2. Feb 15, 2008

### kamerling

There's no force on the whole particle, but there might be forces between the parts of the particle.

3. Feb 16, 2008

Generally they say, they particles do not disintegrate. Like say a bomb. They chemical energy makes it to go off. This, in view of classical mech, is:

The chemical energy converts to kinetic energy.

There's no chem. energy : - no go off

4. Feb 16, 2008

### Riogho

There can't be a particle moving none-at-all, because then we would know it's position and momentum!

5. Feb 16, 2008

### HallsofIvy

Staff Emeritus
In any case, there is no "conservation of kinetic energy" law, nor are "kinetic energy" and "potential energy" the only kinds of energy there are! In order to "disintegrate" into two moving parts, there must have been some kind of internal energy that was converted to the kinetic energy of the parts.

6. Feb 17, 2008

### lugita15

How could one calculate the minimum amount of internal energy required?

7. Feb 17, 2008

### Staff: Mentor

The internal potential energy lost would be exactly equal to the kinetic energy of the resulting system of particles.

8. Feb 17, 2008

### lightarrow

You assumed that the particle had no *external* forces acting on it, infact, after disintegration, the system's centre of mass doesn't move at all.