Kinetics of a Particle:

Kinetics deal with the relations between the motion of bodies and the forces producing these motions. Through the study of the falling bodies. Galileo discovered the first two laws which are commonly known as Newton's laws of motion for a particle. Newton generalized these laws together with the law of universal gravitation.

Newton's laws of motion have been stated in various ways but we can put them in words as follows :

1. A particle acted upon by a balanced force system contains no acceleration.

2. A particle acted upon by an unbalanced force system has an acceleration in line with and directly proportional to the resultant force system.

3. Action and reaction forces among two particles are always equal and oppositely directed.

The reference frame under which Newton's laws are valid is a frame having fixed origin and fixed directions of the axes. This frame is termed as inertial, Newtonian or Galilean frame of reference. For engineering difficulty, inertial frame associated to the surface of the earth is sufficiently accurate.