- #1

ognik

- 643

- 2

If we have 2 (or n) particles, they are a system

**only**if there are internal forces between them? So, no internal forces implies forces on one won't affect the other...

If particles are a system, then the internal forces cancel and we can consider all external forces to be acting through the center of mass, and nett force = total of external forces. The eqtn of motion would be something like ## M \frac{d^2 r}{dt^2} ##?

The 'relative coordinate vector' would be the position vector of the center of mass? What would be the difference between the eqtn of motion in this sense, as opposed to the one above? Enlightenment much appreciated.