Question

On applying a stress of $20\times {10}^8{Nm}^{-2}$ the length of a perfectly elastic wire is doubled. Its Young's modulus will be

• A. $40\times {10}^8{Nm}^{-2}$
• B. $20\times {10}^8{Nm}^{-2}$
• C. $10\times {10}^8{Nm}^{-2}$
• D. $5\times {10}^8{Nm}^{-2}$

Answer 1

The correct option is B $20\times {10}^8{Nm}^{-2}$

$\begin{array}{c}Given:\sigma =20\times {10}^8\\ \Delta l=l\text{unit}\left(cm\right)\\ L=l\text{unit}cm\\ 20\times {10}^8=Y\frac{\Delta \ell }{L}\\ \Rightarrow Y=20\times {10}^{8}N/m^2\\ \text{Hence ans is}\left(B\right)\end{array}$