Question

when force acting on a body has an equal and opposite reaction then why should the body move at all

Answer 1

If the force is apply on object is more than opposite force so object move in the direction of the motion. If equal force apply in both directions so the object does not move in any direction.

Answer 2

WHEN A FORCE ACTING ON A BODY HAVE EQUAL AND OPPOSITE REACTION THEN THE BODY IS NOT MOVE IN ANY DIRECTION.