Laws of Motion

In his 1687 book Principia, Newton initially established his three Laws of Motion: inertia, F = ma, and action-reaction. They explain how a body interacts with the forces acting on it and how those forces cause the body to move. For more than 200 years, experimentation and observation were used to validate Newton's laws, and they are still excellent approximations at the scales and speeds of daily life. They created the groundwork for Newtonian mechanics, another name for classical mechanics. Since Newton, classical mechanics has continued to be a major area of study in both mathematics and physics. It defines how bodies move when they are subject to a system of forces.

The three Laws of Motion explain how a body interacts with the forces acting on it and how it moves in reaction to those forces. At the scales and speeds of daily life, they continue to be excellent approximations. The three laws are listed below.

Number 1, Law of Inertia: Unless forced to do so by external forces, every object remains in a condition of rest or uniform motion in a straight path. Number 2, Law of acceleration: Force is equal to the momentum change (in mV) per change in time. Force equals mass times acceleration for a constant mass or F = ma. Number 3, Law of Action and reaction: There is an equal and opposite reaction to every action.