# Newton's laws of motion

Redirected from Newton's second law of motion
The

Newton first defined these laws in

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**laws of motion**(**laws of inertia**) are the three scientific laws which Isaac Newton described; regarding the motion of bodies. These laws are fundamental to classical mechanics.Newton first defined these laws in

*Philosophiae Naturalis Principia Mathematica*(1687) and, using his newly developed calculus, proved many results concerning "idealised" particles. In the third volume (of the text), he showed how, combined with his Law of Universal Gravitation, the laws of motion would explain Kepler's laws of planetary motion. Newton's laws were modified, in 1916, by Einstein's theory of relativity.**Newton's First Law (Law of Inertia)***Every object persists in its state of rest, or uniform motion (in a straight line); unless, it is compelled to change that state, by forces impressed on it.**A body remains at rest, or moves in a straight line (at a constant velocity), unless acted upon by a net outside force.*

**Newton's Second Law***Force is equal to the change in momentum per change in time.**The acceleration of an object is proportional[?] to the force acting upon it.*

*F*=*ma**F*= force*m*= mass*a*= acceleration.

**Newton's Third Law***Whenever one body exerts force upon a second body, the second body exerts an equal and opposite force upon the first body.**For every action, there is an equal and opposite reaction.**Forces always come in equal pairs.*

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