Newton's Law of Motion

 First law of motion:

 According to Newton's first law of motion :
 "A body tends to continue it's state of rest or of uniform motion unless a force is applied on it ".
 First law of motion is also known as law of inertia 

Inertia:

 "The inability of matter to change it's state of rest or of uniform motion ,is known as inertia".
 inertia of a body depends upon it's mass . Greater the mass of a body larger is it's inertia.

 Second law of motion:

 According to Newton's second law of motion :
               "When an unbalanced force acts on a- body it produces acceleration in the body in it's own direction such that the magnitude of acceleration is directly proportional to the magnitude of force ".

Where "F " represents the unbalanced force and "a" is the acceleration produced in the body of mass "m ". The direction of "a" is same as the direction of "F ".

 Unit of force:

 The unit of force can be defined with the help of Newton's second law of motion . Since,

F = m a

 Therefore the M.K.S unit of force will be kg - m/s^2 which is commonly known as Newton .
 "Force is said to be one Newton (1 N) if it produces an acceleration of 1 m/s^2 in a body of mass 1 kg".
 C.G.S unit of force is "dyne", Whereas the British unit of force is "Pound".
                                       1 Newton = 10^5 dyne.

 Third law of motion:

 According to Newton's third law of motion :
                 "To every action there is always an equal and opposite reaction".
 Action and reaction are two forces which are exchanged between two bodies ,when they interact with each other .