Newton's Laws of Motion/First Law

Physical Law

Newton's first law of motion is one of three physical laws that forms the basis for classical mechanics.

Statement of Law

Every body remains in a state of constant velocity unless it is acted upon by an external unbalanced force.

This of course includes it being stationary, that is, with a constant velocity of zero.

This tendency is sometimes called inertia.

As Isaac Newton himself put it:

A body remains at rest or, if already in motion, remains in uniform motion with constant speed in a straight line, unless it is acted on by an unbalanced external force.

Also known as

This law is also sometimes called the principle of inertia.

It is also often referred to as just Newton's first law.

Also see

• Newton's Second Law of Motion
• Newton's Third Law of Motion

It is worth pointing out that Newton's first law of motion is in fact a special case of Newton's Second Law of Motion, putting $\mathbf F = 0$.

Source of Name

This entry was named for Isaac Newton.

Sources

• 1937: Eric Temple Bell: Men of Mathematics ... (previous) ... (next): Chapter $\text{VI}$: On the Seashore
• 1965: J.W. Leech: Classical Mechanics (2nd ed.) ... (previous) ... (next): Chapter $\text {I}$: Introduction: $(1)$
• 1966: Isaac Asimov: Understanding Physics ... (previous) ... (next): $\text {I}$: Motion, Sound and Heat: Chapter $3$: The Laws of Motion: Inertia
• 1975: Derek F. Lawden: Tensor Calculus and Relativity (3rd ed.) ... (next): Chapter $1$ Special Principle of Relativity. Lorentz Transformations: $1$. Newton's laws of motion
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): Newton's laws of motion