# Question Concerning Coulomb's Law

1. Apr 20, 2007

### Kison

One of Newton's laws(1 or 2) states that every force has an equal and opposite force.

Coulomb's law describes subatomic particles interacting with one another. Electrons repel each-other relative to their distance while attracting protons relative to each-other.

My question is, will the "equal and opposite" part of Newton's law apply in this case? For example, if we have a proton and an electron, will the force of the electron onto the proton fall back onto the electron?

2. Apr 21, 2007

### christianjb

N3L will work for the proton-electron complex. The forces are still equal and opposite (pointing towards eachother).

3. Apr 23, 2007

### quetzalcoatl9

a couple of things:

(a) technically Coulomb's law deals with static charges, it does not (as far as I know) explicitly say anything about subatomic particles. However, we have applied Coloumb's law to subatomic particles with success but:

(b) Newton's law will not hold for an electron-proton systems - QM (and QED) is the only approach (again, that I am aware of) that works. In the Newtonian model, for example, the electron will fall into the proton - and yet we know that this does not happen. The true picture is that of the hydrogen atom, which we get by solving the Schrodinger equation for exactly the system that you describe.

That is not to say that Coulomb's law does not appear in the Hamiltonian for an electron-proton system - infact, it does - but subject to a different equation of motion (the Schrodinger or Heisenberg eqns).

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook