Question

A steel wire of $1\, m$ long and $1\, mm^2$ cross section area is hanged from rigid end when weight of $1 \,kg$ is hung from it then change in length will be (for wire Youngs coefficient $Y=2\times 10^{11}\,N/m^{2}$ ):

• A. 0.5 mm
• B. 0.25 mm
• C. 0.05 mm
• D. 5 mm

Answer 1

Answer: (C)

0.05 mm

Answer 2

Young's coefficient of elasticity $Y=\frac{m g L}{\pi r^{2} \Delta L}$ substituting the values we get $\Delta L=0.05 \,mm$