As was mentioned previously, there is a limit of how much force can be applied to an elastic body for it to then manage to recover its original shape. If this limit is exceeded the "elastic" deformity becomes an "inelastic" deformity. This is known as the "limit of proportionality" or you will sometimes hear it referred to as the "elastic limit".


The extension/compression of the spring, plotted against the force applied on a graph will give you a straight line as long as the elastic limit is not reached (or exceeded). Once we exceed the limit, we will notice that for extra mass applied, the extension/compression will be more than expected.





Once the force is removed, having exceeded the limit of proportionality, the elastic body will not return to its normal shape.