# Simple Vector Notation

1. Jul 25, 2011

### superg33k

1. The problem statement, all variables and given/known data

Does
$$r_{12}$$
mean distance from point 1 to point 2, or point 2 to point 1?

2. Relevant equations

3. The attempt at a solution

2. Jul 25, 2011

### RTW69

Where you typically see this notation is the vector form of Coulomb's law where electric force exerted by a charge q1 on a second charge q2 is written F12

3. Jul 25, 2011

### superg33k

Cheers, I'm using in it Biot-Savat law so same thing really. I always forget it, it drives me nuts! Thanks again.