A metal rod of length ′ L ′ and cross-sectional area ′ A ′ is heated through ′ T ′ degree C . What is the force required to prevent the expansion of the rod lengthwise? [ Y = Young’s modulus of the material of rod, α − coefficient of linear expansion]
A metal rod of length ′ L ′ and cross-sectional area ′ A ′ is heated through ′ T ′ degree C . What is the force required to prevent the expansion of the rod lengthwise? [ Y = Young’s modulus of the material of rod, α − coefficient of linear expansion]

Solution: The correct answer is B.

change\text{ }in\text{ }length:\,~\delta L=L\alpha T

final\text{ }length~\,{{L}_{f}}=L+\delta L

Now, in order to limit the expansion, there must be a force that compresses the rod by \delta L

strain=\frac{\delta L}{{{L}_{f}}}

Y=\frac{F/A}{strain}

F=\frac{YA\alpha T}{1+\alpha T}