6.2 Deformation: Elastic & Plastic Behaviour

A manufacturer produces springs for use in school laboratory investigations. As part of quality control the springs are spot-checked  by measuring the extension produced for certain applied loads.

The graph of the testing data is shown in Fig. 1.1

Fig. 1.1

Use a graphical method to calculate the spring constant of the spring.

Show your working.

Show that the work done in extending the spring up to point A is approximately 0.5 J.

When the spring reaches an extension of 0.046 m, the load on it is gradually reduced to zero.

On the graph in Figure 1.1, sketch how the extension of the spring will vary with load as the load is reduced to zero.

Explain why the graph has this shape.

Without further calculation, compare the total work done by the spring when the load is removed with the work that was done by the load in producing the extension of 0.046 m.  

Explain how this is represented on the graph drawn in part (c).