4 (a) Define the Young modulus of a material.

1. (a)Define the Young modulus of a material.[1]
2. (b)A metal rod is compressed, as shown in Fig. 4.1. [Figure 4.1] The variation with compressive force F of the length L of the rod is shown in Fig. 4.2. [Figure 4.2] Use Fig. 4.2 to
3. (b)(i)determine the spring constant k of the rod, k = .................................................................................. Nm⁻¹[2]
4. (b)(ii)determine the strain energy stored in the rod for F = 90 kN. strain energy = ........................................................................... J[3]
5. (c)The rod in (b) has cross-sectional area A and is made of metal of Young modulus E. It is now replaced by a new rod of the same original length. The new rod has cross-sectional area A/3 and is made of metal of 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 kN.[2]

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