Physical content of Newton's Laws

While the basic principles underlying Newton's theory of motion are often written as equations, we can identify six basic concepts that underlie the theory. Follow the links to read an analysis of each.

• Object egotism: Objects respond to the interactions they feel at the instant they feel them.
• Inertia: The "all effects being equal" state of an object is constant velocity (which could be 0 — an object at rest).
• Interactions: Objects act on each other to change each other's velocities. We call these interactions "forces".
• Superposition: The effects of interactions add like vectors.
• Mass: Interactions are shared over parts of an object.
• Reciprocity: When two objects interact, they each exert forces on each other.

Joe Redish 9/12/11