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Newton's Laws

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The Laws of Motion

In 1687, Sir Isaac Newton published a book called Philosophiae Naturalis Principa Mathematica, which talks about the three laws of motion.

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Newton's First Law (Law of Inertia)
 
Every body continues in its state of rest or of uniform motion unless an external force is applied to it to change that state.  Therefore unless an object is acted upon by an external force it will remain at rest or in a state of constant velocity.
Ex. A golf ball will remain at rest until it is struck by a gold club.
 
Newton's Second Law (Law of Acceleration)
 
F= ma
Newton's second law states that a force that is applied to a body will result in an acceleration of that body of a magnitude proportional to the force, in the direction of the force, and proportional to the object's mass.
Ex. If the same amount of force is applied to a baseball and a bowling ball the baseball (lighter mass) will accelerate much faster than the bowling ball.
 
Newton's Third Law (Law of Reaction)
 
The law of reaction occurs when one body exerts force on another body.  The second body then exerts a reactionary force on the first body. Therefore for every action there is always an equal reaction.
Ex.  A sprinter pushing off of starting blocks.