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JEE Mains · Physics · STD 11 - 10.1, thermonetry,thermal expansion and calorimetry
  • JEE Mains 2019
  • Hard
  • MCQ

At \(40\,^oC\), a brass wire of \(1\, mm\) is hung from the ceiling. A small mass, \(M\) is hung from the free end of the wire. When the wire is cooled down from \(40\,^oC\) to \(20\,^oC\) it regains its original length of \(0.2\, m\). The value of \(M\) is close to ........\(kg\) (Coefficient of linear expansion and Young's modulus of brass are \(10^{-5}/^oC\) and \(10^{11}\, N/m^2\), respectively; \(g = 10\, ms^{-2}\))

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Answer & Solution

Correct Answer

(B) \(9\)

Step-by-step Solution

Detailed explanation

\(\begin{array}{l}
Mg = \left( {\frac{{Ay}}{l}} \right)\,\Delta l\\
Mg = \left( {Ay} \right)\,\alpha \Delta T = 2\pi 
\end{array}\)

It is closest to \(9\)

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