EXAMPLES:
(i) When the book is lying on a table, it exerts a downward force on the table (because of its weight). This force is known as action. The table exerts an upward force on the book known as reaction which is equivalent to the action.
(ii) In our daily life, our walking is the most common example of third law. When we walk we exert a force on the ground backward. This force is known as action. But this force cannot make acceleration in the ground because of its heavy mass. In return ground exerts a force on us forward. This force is known as reaction of the ground. Because of this reactionary force, we move forward.