Question

Which of the following cases will have the greatest strain energy (F is the stretching force, A is the area of cross section and s is the strain)

• A. F = 10 N, A = 1 cm², s = 10^–3
• B. F = 15 N, A = 2 cm², s = 10^–3
• C. F = 10 N, A = $\frac { 1 } { 2 }$cm², s = 10^–4
• D. F = 5 N, A = 3 cm², s = 10^–3

Answer 1

Answer: (B)

F = 15 N, A = 2 cm², s = 10^–3

Answer 2

Strain energy $= \frac { 1 } { 2 } \times \frac { F } { A }$×

strain × AL $= \frac { 1 } { 2 } \times F \times$strain × L

For wire (1) $U = \frac { 1 } { 2 } \times 10 \times 10 ^ { - 3 } \times L = 5 \times 10 ^ { - 3 } L$;

For a given length wire (2) will have greatest strain energy.