Newton reduced the basic principles of mechanics to three laws

Newton's First Law of Motion

Every body continues in its state of rest, or uniform motion in a straight line, unless compelled to change that state by forces imposed on it.

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Newton's Second Law of Motion

The change of motion of an object is proportional to the force impressed upon it, and is made in the direction of the straight line in which the force is impressed.

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Newton's Third Law of Motion

To every action there is always opposed an equal reaction; or, the mutual actions of two bodies upon each other are always equal and directed to contrary parts.

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