Answer to Question 3

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First we need to work out the area:

A = pr2 = p ´ (0.5 ´ 10-3 m)2 = 7.85 ´ 10-7 m2

Stress = F/A = 500 N ¸ 7.85 ´ 10-7 m2 = 6.37 ´ 108 Pa

Strain = e/l = 0.0080 m ¸ 2.5 m = 0.00320

Young’s Modulus = stress/strain = 6.37 ´ 108 Pa  ¸ 0.00320 = 1.99 × 1011 Pa = 2.0 ´ 1011 Pa (2 s.f.)