# Center of force?

1. Jun 8, 2007

### Telos

It's generally common knowledge that gravitational systems have a "center of gravity." Is there such a thing for the other three fundamental forces?

For example, if one had a number of bar magnets on a tabletop, would there be a "center of electromagnetism?" It seems difficult to picture because of electromagnetic charge. Perhaps it only occurs in special cases? Might there be more than one center?

2. Jun 8, 2007

### Cyrus

The center of gravity is a center of force. It is the balance point between all the mass multiplied by gravity, multiplied by is lever arm. m*g*l.

The COG can be extended to any system. You just need to use forces in place of gravitational force. In other words, F=mg in this case. So the moment arms are (m*g*l)=(m*g)*l = F*l

F is any arbitrary force, be it gravitational, electrical, aerodynamic, magnetic.

Center of electromagnetism is meaningless. electromagnetism is not a force, just a word to describe a phenomenon.

The center of gravity is called the fist moment (because theres (l)^1,.... get it first-one).

The second moment is the moment of inertia: m*g*(l)^2 (because theres squared (l)...get it, power of two).

Last edited: Jun 8, 2007
3. Jun 8, 2007

### Telos

Oh, interesting. I took Adv. Physics in high school and this is the first time I've ever heard of a "moment arm." I'm looking it up and learning a lot. Thank you very much.

So is there a "color moment" for the strong force or is it more complicated?

4. Jun 8, 2007

### Cyrus

A moment arm is just a lever arm. Its the between the force and the axis of rotation.

No such thing as a color moment arm. Light has no mass, it cant cause a moment or a force.

5. Jun 8, 2007

### Telos

Oh, I meant the "color charges" for the strong nuclear force.

6. Jun 8, 2007

### Cyrus

I dont know what a color charge is, im not a physicist. -sorry.