Laws of Motion

The three physical laws that lay the foundation for the classical mechanics are the Newton’s Laws of Motion. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces.

Broadly

·        the first law defines the force qualitatively

·        the second law offers a quantitative measure of force.

·        The third states that a single force doesn’t exists.

Newton’s First Law:

In an inertial frame of reference, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.

In simple words, an object tends to be remain at rest or motion until and unless force acts upon it.

Newton’s Second Law:

In an inertial frame of reference, the vector sum of the forces-F on an object is equal to the mass-m of that object multiplied by the acceleration-a of the object.

F=ma

Newton’s Third Law:

When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

In simple words, every action has its equal and opposite reaction.

These three laws of motion were proposed by Sir Isaac Newton in his mathematical principles of natural philosophy which was published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems.

For example in the 3^rd volume of the text Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler’s Laws of Planetary Motion.