Documentation are inside the program. They are collected in a series
of menu items labeled 'Explain'. Click on them anytime. But
you MUST run the tutorials to learn 'freeCAD'. Inside 'freeCAD',
click Explain/Quick Start/ for a list of tutorials on
projectiles, circular motion, relative motion, pendulums,
spring-masses, four-bar linkage, piston-crank, gyro, cam-follower.
Click
here for some screen cam videos.
Example Assemblies
The motion simulation theory is in the journal paper:
Koh, A-S., and Park, J-P. "Object Oriented Dynamics Simulator,"
Computational Mechanics, Jun 1994, 14(3) 277–287.