What is the Relationship Between Strain and Change in Length in Hooke's Law?

[Orodruin]

It should be noted that Hooke's law relates stress $\sigma$ (i.e., the applied force per area) to strain $\epsilon$ as $\sigma = E\epsilon$, where $E$ depends on the material. Thus, from force and cross-sectional area, you can know the strain, but not the change in length (for that you also need to know the original length).

 

[chriscarson]

It should be noted that Hooke's law relates stress $\sigma$ (i.e., the applied force per area) to strain $\epsilon$ as $\sigma = E\epsilon$, where $E$ depends on the material. Thus, from force and cross-sectional area, you can know the strain, but not the change in length (for that you also need to know the original length).

Actually I have the hooke s law in my notes to study , but not easy to understand that part either.