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JEE Mains · Physics · STD 11- 8. mechanical properties of solids

A compressive force, \(F\) is applied at the two ends of a long thin steel rod. It is heated, simultaneously, such that its temperature increases by \(\Delta T\). The net change in its length is zero. Let \(l\) be the length of the rod, \(A\) its area of cross- section, \(Y\) its Young's modulus, and \(\alpha \) its coefficient of linear expansion. Then, \(F\) is equal to

  1. A \({l^2}\,Y\alpha \Delta T\)
  2. B \(lA\,Y\alpha \Delta T\)
  3. C \(A\,Y\alpha \Delta T\)
  4. D \(\frac{{AY}}{{\alpha \Delta T}}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(A\,Y\alpha \Delta T\)

Step-by-step Solution

Detailed explanation

Due to thermal exp., change in length \(\left( {\Delta l} \right)\) \( = l\alpha \Delta T\) \(...(i)\) \(Young's\,modulus (Y)\) \( = \frac{{Normal\,stress}}{{Longitudinal\,strain}}\) \(Y = \frac{{F/A}}{{\Delta l/l}} \Rightarrow \frac{{\Delta l}}{l} = \frac{F}{{AY}}\)…
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