(b) Fig. 1.1 shows a graph of the stretching force F acting on a spring against the extension x of the spring.

(iii) The limit of proportionality of the spring is reached at an extension of 50 mm.
Continue the graph in Fig. 1.1 to suggest how the spring behaves when the stretching force is increased to values above 125N.

(iv) Another spring has a smaller value of k. This spring obeys Hooke's law for
extensions up to 80 mm.
On the grid of Fig. 1.1, draw a possible line of the variation of F with x for this spring.