Question

A metal rod of young's modulus $5\times {10}^{9}N/m^2$ undergoes strain of 0.04%. The energy stored in unit volume of rod is

• A. 300J
• B. 200J
• C. 400J
• D. 100J

Answer 1

The correct option is C 400J

$\frac{U}{V}=\frac{1}{2}\left(Stress\right)\left(Strain\right)$
$=\frac{1}{2}Y(Strain{)}^2$
$=\frac{1}{2}(5\times {10}^9)(4\times {10}^{-4}{)}^2$
$=\frac{1}{2}5\times {10}^9\times 16\times {10}^{-8}=\frac{16\times 5\times 10}{2}=400J$