Rankers Physics
Topic: Solid and Fluids
Subtopic: Solids

A wire of length $L$ area of cross section $A$ is hanging from a fixed support. The length of the wire changes to $L_1$ when mass $M$ is suspended from its free end. The expression for Young's modulus is:

(2020)

$\frac{Mg(L_1 - L)}{AL}$
$\frac{MgL}{AL_1}$
$\frac{MgL}{A(L_1 - L)}$
$\frac{MgL_1}{AL}$

Solution:

Young's modulus $Y = \frac{\text{Stress}}{\text{Strain}} = \frac{Mg/A}{\Delta L/L}$. Here, the change in length $\Delta L = L_1 - L$. Substituting this gives $Y = \frac{MgL}{A(L_1 - L)}$.

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