No force implies constant velocity. Net force implies acceleration. Demonstrations of Newton's laws. Action-reaction, free fall. Historical perspective, early Greek concepts, the renaissance.
Source is mass.
Universality, inverse square law, force fields. A direct demonstration of the attraction due to gravity between two small objects. 8 omit Kepler. Lack of evidence for magnetic monopoles. The force due to a magnetic field on a moving charged particle will be directly demonstrated, the aurora, sunspots.