HOOKE'S LAW
If we again consider the force separation graph from 2.3 , we can see that for solids, where the atomic separation is close to that at absolute zero, there is an almost straightline relationship between increasing separation and the (-ve) force resisiting it. Hence Hookes Law for solids states that upto a maximum force (the limit of proportionality) the extension of a wire is proportional to the applied force.

Note:

• Temperature increases in a polymer material lead to a rise in its Young's modulus, as the increased vibrations of its long chain molecules, causes more "tangles" between them and hence they become harder to straighten.