He stated his observation as "Ut tensio, sic vis" - - As the extension, so is the force. This linear elastic response has been formalized into the stress/strain relationship known as Hooke's Law: ...

Record each stretching force in N and the corresponding length of the spring. The extension is the new length minus the unloaded length. Figure caption, Graph showing Hooke's Law, force is plotted ...

But what makes a spring stay… springy? It all comes down to force and Hooke’s Law, as Professor Brian Cox explains with a quick physics lesson.