The variation with extension x of the force F applied to a spring is shown in Fig. 4.1. [Figure 4.1] The spring has an unstretched length of 0.080 m and is suspended vertically from a fixed point, as shown in Fig. 4.2. [Figure 4.2] A block is attached to the lower end of the spring. The block hangs in equilibrium at position X when the length of the spring is 0.095 m, as shown in Fig. 4.3. [Figure 4.3] The block is then pulled vertically downwards and held at position Y so that the length of the spring is 0.120m, as shown in Fig. 4.4. The block is then released and moves vertically upwards from position Y back towards position X. [Figure 4.4]