Question

The work done in twisting a steel wire of length 25 cm and radius 2mm through $45^{o}$ will be$(\eta = 8 \times 10^{10}N/m^{2})$

• A. 2.48 J
• B. 3.1 J
• C. 15.47 J
• D. 18.79 J

Answer 1

Answer: (A)

2.48 J

Answer 2

$W = \frac{1}{2}C\theta^{2} = \frac{\pi\eta r^{4}\theta^{2}}{4l} = \frac{3.14 \times 8 \times 10^{10} \times (2 \times 10^{- 3})^{4} \times (\pi/4)^{2}}{4 \times 25 \times 10^{- 2}} = 2.48J$