Explanation
(a)(i) Stress is force per unit cross sectional area, while strain is extension over original length
(ii) Stress has unit of Nm\(^{-2}\) while strain has no unit.
(b) Work done on the cord = \(\frac{1}{2}\) Fe
= \(\frac{1}{2}\) x 40 x 0.05 = 1.0J

