(a)[1]
Define the Young modulus of a material.
(b(i))[2]
A metal rod is being compressed, as shown in Fig. 4.1. Fig. 4.2 shows how the rod’s length $L$ changes with compressive force $F$. Use Fig. 4.2 to find the spring constant $k$ of the rod.
(b(ii))[3]
Find the strain energy stored in the rod when $F = 90\,\text{kN}$.
(c)[2]
The rod in (b) has cross-sectional area $A$ and is made of metal with Young modulus $E$. It is now replaced by a different rod with the same original length. The new rod has cross-sectional area $\frac{A}{3}$ and is made of metal with Young modulus $2E$. The compression of the new rod obeys Hooke’s law. On Fig. 4.2, sketch the variation with $F$ of the length $L$ for the new rod from $F = 0$ to $F = 90\,\text{kN}$.