Question

An elongation of 0.4% in a wire of cross section area ${10}^{-6}{m}^2$ causes a restoring force of 80 N. Then, the young's modulus of wire is___$\left(N/m^2\right)$.

• A. $5\times {10}^9$
• B. $2\times {10}^{10}$
• C. $8\times {10}^{10}$
• D. $3\times {10}^3$

Answer 1

The correct option is B $2\times {10}^{10}$

$Y=\frac{Stress}{Strain}$
$Y=\frac{Stress}{Strain}=\frac{\frac{80}{{10}^{-6}}}{\frac{0.4}{100}}$
$=\frac{80\times 100}{{10}^{-6}\times 0.4}=\frac{8\times {10}^3}{4\times {10}^{-7}}=2\times {10}^{10}$