FIG. 1.

Schematic diagram of a linearly elastic solid. A force ( $\stackrel{\rightharpoonup }{F}$) is applied to the area ( $A$) of one face of a linearly elastic solid. This stress ( $\sigma$) in turn causes a change in length ( $\Delta L$) relative to the initial length of the solid ( $L_0$), also known as a strain ( $ϵ$). The ratio of stress to strain yields the Young's modulus of the elastic solid ( $E$), a measure of intensive stiffness.