# Force between two magnets as related to distance

1. Apr 10, 2008

### Magnet4less

Hello,
I am new to the forum, thus please be patient with me.

I have a little bit of a problem....

Currently working with magnets. Basically, I need to derive an equation for the attractive/repulsive force between two magnets given a distance between them. The most important thing is that these magnets not interfere with eachother, in other words I need the attractive/repulsive force to be zero.

Thoughts so far....
- Newton's Universal Gravity equation
- F = GMm/R²
- manipulate the pull force of the magnet to derive a mass...divide pull force of magnet by 9.8m/s^2
- need to set F to an infinitely small amount and solve for R

I do not get offended very easily, so if you need to completely slam my thoughts so far in order to get me on the right track, I understand.

2. Apr 11, 2008

### tiny-tim

Welcome to PF!

Hi Magnet4less ! Welcome to PF!

I'm not sure what you mean … do you mean you want the gravitational attraction between the magnets to be balanced by their magnetic repulsion?

(but if so, why are you using the value of g here on Earth?)

3. Apr 15, 2008

### Magnet4less

I'm trying to figure out how close I can place the magnets to one another without them visibly affecting each other.

4. Apr 19, 2008

### tiny-tim

Hi Magnet4less!

The exact formula for the force between two bar magnets is in wikipedia: