A man pulls on a box with 50 N of applied force while another man pushes on the box from the opposite direction with 60 N of applied force. The box will stand still.
Force with which a man pulls a box, F = 50 N (one side)
Force with which pushes on the box, F' = 60 N (in opposite direction)
The forces acting on the box are unbalanced. It means that the force acting in one side is more or less then force in other side. As a result the box will move.
