Newton's 3 Laws of Motion
1. Every body continues in its state of rest, or of uniform motion in a [straight] line, unless it is compelled to change that state by forces impressed upon it. (link to NASA's page on the first law)
2. Force (F) is equal to the change in momentum (m) per change in time. For a constant mass, force equals mass times acceleration F = ma (link to NASA's page on the second law)
3. For every action there is an equal and opposite reaction.
