(a)[1]
Define Young modulus in terms of stress and strain.
(b(i))[3]
The Young modulus of steel is $1.9 \times 10^{11}\,\text{Pa}$. The Young modulus of copper is $1.2 \times 10^{11}\,\text{Pa}$. A steel wire and a copper wire each have the same length and cross-sectional area. Equal forces are applied to the two wires. Use the definition of the Young modulus to determine the ratio $$\frac{\text{extension of the copper wire}}{\text{extension of the steel wire}}.$$
(b(ii))[1]
The two wires are each stretched by a force. Both wires obey Hooke’s law. On Fig. 3.1, sketch a graph for each wire to show how force varies with extension. Label the steel line $S$ and the copper line $C$.