Fundamental Principles in Mechanics

Fundamental Principles

Six fundamental principles, which are based on experimental evidence, are used in mechanics. They are Newton's three laws of motion, Newton's law of gravitation, parallelogram law for addition of forces and the law of transmissibility of force.

i) Newton's first law

iii) Newton's third law

v) Parallelogram law

ii) Newton's second law

iv) Newton's law of gravitation

v) Law of transmissibility of force

i) Newton's first law: 

Every body tries to be in its state of rest or of uniform motion along a straight line unless it is acted upon by an external unbalanced force.

ii) Newton's second law: 

The rate of change of momentum of a body is directly proportional to the force acting on it and takes place in the direction of the force.

iii) Newton's third law: 

Every action has equal and opposite reaction.

iv) Newton's law of gravitation: 

Every body in the universe attracts every other body with a force whose magnitude is directly proportional to the product of the two masses and inversely proportional to square of the distance between them.

v) Parallelogram law: 

If two vectors are represented in magnitude and direction by two adjacent sides of a parallelogram, their resultant is represented in magnitude and direction by the diagonal of the parallelogram drawn from the common point.

vi) Law of transmissibility of force: 

Force can be transmitted from one point to another on its line of action without causing any change in the state of its motion.