Dear all , I have a very simple question. i am pushing a wall.wall didn't move an inch. I exerted a force(as much as i could-see iam even sweating).But the calculations and science saying NO force.,since ,by defenition,force = mass x acceleration. So what shall i call the thing,i was doing with the wall?As i understand,i thought push is a sort of force.So i thought i was exerting a force to the wall. why this injustice is happening to me? could anybody explain me?