Effects of forces — Sketch

How do you investigate and interpret the load-extension graph of a spring?

A spring is clamped vertically with its original length measured using a ruler; known loads (masses) are added one at a time and the extension (new length minus original length) is recorded for each, then plotted with load on the y-axis and extension on the x-axis. The graph is a straight line through the origin up to the limit of proportionality, showing extension is proportional to load, after which the line curves as the spring stretches disproportionately more.