For the deformation of a wire under tension, define (i) stress,

1. (a)(i)For the deformation of a wire under tension, define (i) stress,[1]
2. (a)(ii)(ii) strain.[1]
3. (b)(i)A wire is fixed at one end so that it hangs vertically. The wire is given an extension x by suspending a load F from its free end. The variation of F with x is shown in [Figure 3.1]. The wire has cross-sectional area 9.4 × 10⁻⁸ m² and original length 2.5 m. Describe how measurements can be taken to determine accurately the cross-sectional area of the wire.[3]
4. (b)(ii)Determine the Young modulus E of the material of the wire.[2]
5. (b)(iii)Use [Figure 3.1] to calculate the increase in the energy stored in the wire when the load is increased from 2.0N to 4.0N.[2]
6. (c)The wire in (b) is replaced by a new wire of the same material. The new wire has twice the length and twice the diameter of the old wire. The new wire also obeys Hooke's law. On [Figure 3.1], sketch the variation with extension x of the load F for the new wire from x = 0 to x = 0.80 mm.[2]

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