The motions of bodies are based on three laws that were experimentally verified by Newton and should hold in any inertial frame:

- An object at rest tends to stay at rest, and an object in motion
tends to stay in motion with fixed speed, unless a nonzero
resultant
^{13.8}force acts upon it. - The relationship between a body mass , its acceleration , and an applied force is .
- The interaction forces between two bodies are of equal magnitude and in opposite directions.

Steven M LaValle 2012-04-20