Are there documentation, tutorials or examples?

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.