NEWTON'S 2ND LAW OF MOTION

When an unbalanced force acts upon a body, it is accelerated in the direction of force. The magnitude of acceleration is directly proportional to the applied force and is inversely proportional to the mass of body.
MATHEMATICALLY
Combining (i) and (ii)
....
a = k (F)(1/m) here constant k=1
a= (1)(F)(1/m) Or
SECOND STATEMENT
With the help of above equation 2nd law of motion can be expressed as:
THE NET FORCE ACTING ON A BODY IS EQUAL TO THE PRODUCT OF THE MASS OF BODY AND THE ACCELERATION PRODUCED IN IT.
NEWTON'S 3RD LAW OF MOTION
STATEMENT:
"To every action there is a reaction equal in magnitude but opposite in direction"
OR
"When a body exerts a force on another body, the second body also exerts a force on the first body of same magnitude but in the opposite direction"
FACTION = -FREACTION
Force exerted by one body is called ACTION and the force exerted by the second body is called    REACTION.
EXAMPLES:    (1) Motion of rocket: fuel burns rapidly, exerts force in downward direction and rocket moves upward        as a reaction.    (2) Book lying on a table: weight of the book on the surface is action and the force exerted by the          surface (R) is the reaction.                         R = -W    (3) Walking on a street    (4) Motion of helicopter