# Question concerning the direction of the vector r in the FL

1. Apr 22, 2014

### 3102

Hello! I've got a question concerning the direction of the vector r in the Feynman Lectures of Physics in Chapter 13.3 http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S3

Which direction does the vector r in equation 13.5 point in?
The long equation before equation 13.6 suggests that it should point from $m_{j}$ to $m_{i}$.

Is that correct?

2. Apr 23, 2014

### UltrafastPED

The convention is given in figure 13.2: the vectors point from 1 to 2.

3. Apr 23, 2014

### dauto

Do you mean 13.15 and 13.16?

4. Apr 23, 2014

### 3102

The vector should be the same in both equations.