What is Stress? are force and stress the same? Not for us it's rather tricky to say they're the "same" like it can be said elsewhere. Stress = Force/ Area if either changes the overall stress changes ( area will change more often than force) like saran wrap it seems to stretch forever until you stab it with a sharp object this is because the area of force applied changes ( big to small). Normal stress is perpendicular to the plane in 2D planes and shear stress is acting along the 2D plane, parallel. These are sometimes called "tractions" this is matrix algebra stuff. The pole is the normal stress and one along the earth that cause earthquakes are the shear stress. The area of the plane is important.