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Mechanics is the branch of physics that concerns the effect of force on bodies. It is classified into two branches, i.e., statics and dynamics.

It is the branch of mechanics that studies the bodies at static equilibrium (a state where bodies are at rest) under the action of forces.

It is the branch of mechanics that studies the bodies at motion under the action of forces.
Dynamics is further classified as follows.
1. Kinematics:

It studies the motion of bodies without considering the cause of motion.
2. Kinetics:

It deals with the motion of bodies considering the cause of motion.
Aristotle, a Greek philosopher and scientist, found that the natural state of earthly bodies is ‘rest’.
He proposed that a moving body usually comes to rest without any external impact of the force. Such motions are called ‘Natural motion’ (Force independent).
He also stated that a force (a push or a pull) is required to make the bodies move from their natural state (rest) and act contrary to their own natural state called ‘Violent motion’ (Force dependent).
Further, when two different mass bodies are dropped from a height, the heavier body falls faster than the lighter one.
Galileo Galilee proposed the following concepts about forces, motion and inertia of bodies:
  • The natural state of all earthly bodies is either the state of rest or uniform motion
  • A body in motion will remain in the same state of motion as long as no external force is applied. 
  • When a force is applied to bodies, they resist any change in their state. This property of bodies is called ‘Inertia’. 
  • When dropped from a height in a vacuum, bodies of different sizes, shapes, and mass fall at the same rate and make contact with the ground at the same time.