So I've been playing with Scratch recently to generate simulations and animations. It's really easy to use, there are online tutorials, and I bet you could do some really cool things with it.

Here is a link to the download:

http://scratch.mit.edu/

I'll also upload some of my projects so you can see how to code for different situations. You need to be running Scratch to open them.

constant velocity/constant acceleration.
constant velocity x, then constant velocity x and y.
for every force there is an equal and opposite force.
constant velocity for one sprite, constant acceleration for the other.
constant velocity/constant acceleration. (I bet I could make this one better)