Question

What is the energy stored per unit volume in copper wire of uniform cross-section of length $1.5m$ when it is stretched to a length of $1.51m$ by a stress of $3\times {10}^{2}N/m^2$ ?

• A. $1J/m^3$
• B. $0.1J/m^3$
• C. $2J/m^3$
• D. $0.2J/m^3$

Answer 1

Answer: (A)

$1J/m^3$

Energy stored per unit volume $=\frac{1}{2}\times stress\times strain$

$Stress=3\times {10}^{2}N/m^2$

$Strain=\frac{△l}{l}=\frac{0.01}{1.5}=$

$=\frac{1}{2}\times 3\times {10}^2\times \frac{0.01}{1.5}=1J/m^3$