고체역학 (Beer) — Stress and Strain—Axial Loading: Problem 2.7

2.7 A nylon thread is subjected to a 2-lb tension force. Knowing that \(E = 0.5 \times 10^6 \text{ psi}\) and that the maximum allowable normal stress is \(6 \text{ ksi}\), determine (a) the required diameter of the thread, (b) the corresponding percent increase in the length of the thread.