Question

if newton's third law is true then why does any object ,like chair, move? because action force is equal to reaction force then the resultant force is zero.

Answer 1

see newton law says action force equals reaction force but the forces act on different object .
when i push you , i apply a force on your body and the reaction force is applied on my body not yours .
so you have experienced one force and i have also experienced one force and it is not cancelled out .

when equal and opposite forces act on same body the net force equals zero