Drag elements around with gravity effect

I want to accomplish something similar to what photoshop.com has and this site here: http://mrdoob.com/projects/chromeexperiments/google_gravity/

Does anyone know how to do this with javascript (pre开发者_如何学Pythonferably jquery) ?

A jPhysics demo can be found online at http://www.inf.ufrgs.br/~rcpinto/physics/ and downloaded from http://plugins.jquery.com/project/jphysics or from Google at http://code.google.com/p/jqueryphysics/

I think the google example used Box2Djs. I have used box2d for python and its great.