(a) Distinguish between stress and strain as used in elasticity.
(b) When a force of 40 N is applied to the free end of an elastic cord, an extension of 5cm is produced in the cord. Calculate the work done on the cord.
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