Compute the force between two identical dipoles. See Problem P63 on page 544 to set up the problem. Explain why this result makes sense by comparing it to the force between two point charges and the force between a point charge and a dipole, in terms of the relationship to the distance between the two objects.
P64 shows the two dipoles that are parallel and in the same orientation, separated by a distance r from their centers and have a distance of s between them. The charges that make up the dipole are -q and +q.
The Attempt at a Solution
I thought I would calculate the force on each charge of the dipole on the right by using the equation above and F=Eq. Then I would add the two. For r, I'm confused about weather I should use (r+s/2) and (r-s/2).When I tried this, I couldn't find a way to simplify to the desired answer which I know is 6kq^2s^2/r^4.
Thanks so much for any help in advance.