Simple, open source, 2D impulse based physics engine for educational use. http://gamedev.tutsplus.com/tutorials/implementation/custom-2d-physics-engine-oriented-rigid-bodies
Impulse Engine
Created by Randy Gaul
Impulse Engine is a small 2D physics engine written in C++. The engine is intended to be used in an educational manner by other looking to learn the inner workings of physics engines.
Should build in Windows with Visual Studio 2008-2012. Should build on Linux and OSX platforms with the use of C++11 std::chrono. Thanks to whackashoe for the cross-platform port.
If you have any questions feel free to contact Randy at: r dot gaul at digipen dot edu.
http://randygaul.net