Question

A force of 2N stretches an elastic material by 15mm. What additional force will stretch the material 17mm , assume that the elastic limit is not exceeded.

Answer 1

Find the stiffness of the material from the given data: 2 N stretch it for 15 mm:

$$k=\frac{F}{x}=\frac{2}{0.015}=133.3\text{ N/m}.$$

For 17 mm, the force required is

$$F_1=kx_1=133.3\cdot0.017=2.267\text{ N}.$$

The additional force, therefore, is

$$\Delta F=F_1-F=0.267\text{ N}.$$