Steel wire of length ' $L$ ' at $40^{\circ} C$ is suspended from the ceiling and then a mass ' $m$ ' is hung from its free end. The wire is cooled down from $40^{\circ} C$ to $30^{\circ} C$ to regain its original length ' $L$ '. The coefficient of linear thermal expansion of the steel is $10^{-5} /{ }^{\circ} C$, Young's modulus of steel is $10^{11} N / m ^2$ and radius of the wire is $1 \ mm$. Assume that $L \gg$ diameter of the wire. Then the value of ' $m$ ' in $kg$ is nearly
  • A$3$
  • B$4$
  • C$5$
  • D$6$
IIT 2011, Advanced
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