# Newton's Laws of Motion

## Physical Laws

Newton's Laws of Motion are a set of three physical laws that form the basis for classical mechanics.

### First 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.

### Second Law

The total force applied on a body is equal to the derivative with respect to time of the linear momentum of the body:

 $\ds \mathbf F$ $=$ $\ds \dfrac {\d \mathbf p} {\d t}$ where $p$ denotes linear momentum $\ds$ $=$ $\ds \map {\dfrac \d {\d t} } {m \mathbf v}$ where $m$ denotes mass and $\mathbf v$ denotes velocity

### Third Law

To every force there is always an equal and opposite force.
That is, the forces of two bodies on each other are always equal and are directed in opposite directions.

## Also known as

Newton's Laws of Motion can also be referred to as just the Laws of Motion.

## Source of Name

This entry was named for Isaac Newton.

## Historical Note

Newton's Laws of Motion were expounded by Isaac Newton in $1687$ in his Philosophiae Naturalis Principia Mathematica.