Javascript Library For Modular and Extendable Physics Engine - PhysicsJS

PhysicsJS is a modular, extendable, and easy-to-use physics engine for javascript.

Main Features:

Use as an AMD Module (requireJS), or global namespace.
Modular! Only load what you need. The core library is only 31k minified.
Extendable! Don’t like the collision detection algorithm? Replace it with your own!
Not tied to a specific renderer. Display it in DOM, HTML5 Canvas, or whatever…
Easy! It’s a library written IN javascript… not C compiled into javascript. The syntax is familiar for javascript developers.
Extensions to support points, circles, and arbitrary convex polygons.
Extensions to support constant gravity, newtonian gravity, collisions, and verlet constraints.