Imagine pulling on the end of a long, fixed rod, applying [[Force|tension]] to the member. According to Newton’s 3rd law, by applying this force the rod will necessarily react by applying an equal and opposite force internally. This resulting reaction force will create what is known as a normal [[Stress|stress]] along the rod. Normal stress acts axially along an object, the acting force is parallel to the [[Normal|normal]] of the cross-section of interest. ![[normal_stress.png]] Average normal stress can be defined: $\sigma_{avg}=\dfrac{F}{A}$