1.30 understand that the initial linear region of a force-extension graph is associated with Hooke’s law

Hooke's law stated that the force needed to extend (or compress) a spring is proportional to the distance it is extended (or compressed).

a force extension graph shows how much a material stretches in proportion to how much force is applied.

The initial linear region is the straight diagonal line showing a linear correlation between force and extension, basically meaning that they increase at the same rate (this is Hooke's law).

At some point, the graph will curve, this is when the spring reaches its elastic potential, the extension and force are no longer proportional.