Funny, this reminds me of all those old 2d mass-spring engines. I believe there was a cool one like asteroid where you could shear off one of your engines making your ship spin around. It was open source too. Can't remember the name.

EDIT: Ah, found it: http://www.alecrivers.com/physical/overview_physics.htm

There is even a older one that was an form-based application for windows where you could edit particles and connections. Pretty fun.