by Ramona Taylor

Created on: November 04, 2009   Last Updated: January 02, 2010

In 1687, Sir Isaac Newton's Three Laws of Motion were first published in the "Principia Mathematica Philosophiae Naturalis." With their introduction, Newton offered an explanation of how and why objects move.  His laws create new concepts that redefined the science of mechanics.

Newton's First Law of Motion

According to Newton's first law,  an object at rest will remain at rest until a force acts upon it. His law clarifies that an object in constant motion will remain in constant motion until a force acts upon it. The law basically explains that motion is impacted by external forces.

To understand the clearness of this rule, consider and object in motion. Consider that movement of balls on a pool table. You set your balls in a rack. They remain motionless in the center of the table. However, once the strike the set of balls, they scatter in different directions. The rolling ball applied a force which caused the other balls to be affected. The balls stopped when they hit the edges of the table (another force) or collided with other balls.

Newton's first law was a restatement of Galileo's observation on objects in motion. In Galileo's time, his thoughts on science often brought him in conflict with the Church. However in Newton's Principia, Newton gave credit to the elder scientist, who died the year Newton was born.

Newton's Second Law of Motion

Newton's Second Law of Motion explains the relationship of forces, mass and speed. Similar to the first law of motion, this second concept explains why speeds and the forces are related to acceleration and deceleration. The Second Law of Motion states that the acceleration of an object produced by a force is directly related to the magnitude of the force. Newton offered a mathematical formula to explain this law- F=ma (where F represents force, M represents mass, A represents acceleration.)

Newton's Second Law is intuitive and easy to demonstrate. Compare the movement of a bowling ball as compared to a tennis ball. If a person hit a tennis ball with the same force as a bowling ball, the heavier object will not move as far. The object with the heavier mass will need more force to have the same acceleration as the smaller object.

In knowing any of the values for mass, speed, and/or force, a person could determine unknown values.  Using this formula, scientists could calculate the effect of forces and predict everything from the movement of falling objects and the motion of planets.

Newton's Third Law

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