Question

A steel wire of length $7m$ and cross section $1{mm}^2$ is hung from a rigid support with a steel weight of volume $1000cc$ hanging from the other end. Find the decreases in the length of wire, when steel weight is completely immersed in water.
$(Y_{steel}=2\times {10}^{11}{N/m}^2)$
Density of water$=1g/c.c)$

Answer 1

Given, $Length=7m,Cross-section=1mm,Volume=1000cc$

So $y=2\times {10}^{1}1N/m$

The density of the water $=19cc,density=\frac{mass}{volume}\Rightarrow y=\frac{mgL}{\pi r^2\Delta L}=\frac{1\times 10\times 7}{1}{0}^{-6}\times y=\frac{70\times {10}^6}{2\times {10}^{11}}=3.5\times {10}^{-5}\Rightarrow \Delta L=0.35mm$