Thanks for the comments. I've incorporated Graham's suggestsions. While Jim's is very interesting I also think it's a much more advanced topic that deserves its own post (maybe from Jim). I've done some tweaking & typo correction. The other thing I've done is add wikipedia links for a lot of the terms used.
The big remaining problem is the initial car example. Ideally I'd like something as easy to understand with a weird effect that's easy to model but difficult to explain **which only uses physics**. However, I'm drawing a blank on what that could be, so it may be best to just stick with the existing example.
I think all the key content is there, but it does need some more polishing of the wording.