Interestingly, though I have no experience with this at all, I intuitively assumed whta Alan said. Upon reflection, I think that's because I can remember playing with magnets as a boy. You could set them on a table (arbitrary numbers here, just for example's sake) say an inch apart and they'd just sit there. Move them a fraction of an inch closer, and "SNAP" they're joined at the hip. It was like going from no magnetism, to intense magnetism, with only a slight change in distance.
Moving them apart was the same. Lots of attraction as you moved them apart to, suddenly, no attraction. The magnetism fell off rapidly, not in a linear manner.
You can learn a lot about physics by experimentation as a boy. Such as how fast a body (your own) call fall from the rafters of the unfinished new house you're playing in, all the way to the basement. Trust me! It's VERY fast!
