Question

A steel rod has a radius $ R = 9.5\, mm $ and length $ L = 81 \,cm $ . A force $ F = 6.2 \times 10^4\, N $ stretches it along its length. What is the stress in the rod?

• A. $ 0.95 \times 10^8 \,N/m^2 $
• B. $ 1.1 \times 10^8 \,N/m^2 $
• C. $ 2.2 \times 10^8 \,N/m^2 $
• D. $ 3.2 \times 10^8 \,N/m^2 $

Answer 1

Answer: (C)

Stress $ = \frac{F}{A}$
$ = \frac{6.2\times 10^4}{\pi r^2}$
$ = \frac{6.2\times 10^4}{3.1\times (9.5)^2 \times (10^{-3})^2}$
$ = 2.2 \times 10^8\,N/m^2$