# The meaning of the relative strength of forces

1. Feb 26, 2009

### Tac-Tics

It's common to hear people say that gravity is a "weak force" and that it is "32 times weaker than the weak nuclear force." But what does that even mean, if it has any meaning at all. The gravity on a particle is proportional to its mass. The electric force on an object is proportional to its charge. To make a statement about relative strengths, that would mean you're making an implicit statement about the relationship between an object's charge and mass, right?

2. Feb 26, 2009

### Nabeshin

Here's a simple illustration using simplifed forms of the gravitational and electric forces:

$$F_{g}=G\frac{m_{1}m_{2}}{r^{2}}$$

$$F_{e}=k\frac{q_{1}q_{2}}{r^{2}}$$

If we compare the constants of proportionality, k and G, we find that k=10^20 G. It's basically saying that per whatever unit the force uses to measure its strength, one force is much stronger than another.

3. Feb 26, 2009

### Tac-Tics

Yeah, but that's comparing apples (mass) to oranges (charge). The units are different, so you can't simply divide and find the ratio of the strengths... you're left with a conversion factor of kg/C or something.

4. Feb 26, 2009

### Nabeshin

You are of course right. That example was pretty terrible and I was making light of what is a much more complicated situation. I don't fully understand this myself but after looking around I think it has something to do with the relative coupling constants for the four fundamental forces.

See:http://en.wikipedia.org/wiki/Coupling_constant