Newton's Laws of Motion

The first law of motion concentrates on a state of constant motion but adds unless an outside influence, force, acts on it. Force produces a change in the state of motion (velocity describes a body's motion); that is, an acceleration. Newton found that the greater a body's mass the greater the force required to overcome its inertia and mass is taken as a quantitative measure of a body's inertia. He also found that applying equal force to two different masses, the ratio of their accelerations was inversely proportional to the ratio of their masses. Newton's second law of motion is thus stated: A net force acting on a body produces an acceleration; the acceleration is inversely proportional to its mass and directly proportional to the net force and in the same direction.

This law can be put mathematically F = ma where F is the net force, m is the mass, and a the acceleration. The second law is a cause-effect relationship. The net force acting on a body is determined from all forces acting and the resultant acceleration calculated (assuming a known mass). From the acceleration, velocity and distance traveled can be determined for any time.