Newton's Laws of Motion

Newton's Laws of Motion

Isaac Newton was born in 1642, the year Galileo died.

Newton's three laws are listed below the way they are usually formulated

"Newton's three Laws of Motion" are the foundation of the theory of motion--e.g., of orbits and rockets.
This section discusses two concepts on which they are based:
Force and Inertia

The 3 Law of Motions are as below

1. In the absence of forces, ("body") at rest will stay at rest, and a body moving at a constant velocity in a straight line continues doing so indefinitely.


2. When a force is applied to an object, it accelerates. The acceleration a is in the direction of the force and proportional to its strength, and is also inversely proportional to the mass being moved. In suitable units:


a = F/m

or in the form usually found in textbooks

F = m a

More accurately, one should write

F = ma

with both F and a vectors in the same direction (denoted here in bold face). However, when only a single direction is understood, the simpler form can also be used.

3. "The law of reaction," sometimes stated as "to every action there exists an equal and opposite reaction." In more explicit terms:


Forces are always produced in pairs, with opposite directions and equal magnitudes. If body #1 acts with a force F on body #2, then body #2 acts on body #1 with a force of equal strength and opposite direction.