Newton's Laws of Motion:
Motion has been described in many different ways over the centuries...
Aristotle believed in two basic forms of motion, natural and violent motion. (Also see Theophrastus, a pupil of Aristotle's)
Galileo experimented with, among other things, falling and projectile bodies (motion in a vertical plane) and also things rolling, sliding, and generally moving along surfaces (motion in a horizontal plane). Galileo also outlined the principles of Inertia, upon which our next scientist built his 1st Law...
Sir Isaac Newton, in his tome, Principia Mathematica, gave us the 3 basic Laws of Motion which really defined and improved upon all previous scientific thought about the subject. These laws are as follows:
Newton's 1st Law of Motion:
Objects continue in a state of rest, or in motion in a straight line at constant speed unless acted upon by an outside force.
Newton's 2nd Law of Motion:
(a) An object's acceleration is produced by a net force (combination of forces).
(b) This acceleration is directly proportional to the magnitude of the net force, is in the same direction as the net force.
(c) The acceleration is also inversely proportional to the mass of the object (seen in the formula F=ma).
Newton's 3rd Law of Motion:
For each force exerted by an object on another object, there is an equal force in the opposite direction. (This law is often stated "For every action, there is an equal and opposite reaction")
Momentum & Impulse