Four identical hollow cylindrical columns of mild steel support a big structure of mass $50,000 \;kg$. The inner and outer radii of each column are $30$ and $60\; cm$ respectively. Assuming the load distribution to be uniform, calculate the compressional strain of each column.

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Total force exerted, $F=M g=50000 \times 9.8 N$

Stress $=$ Force exerted on a single column $=\frac{50000 \times 9.8}{4}=122500 N$

Young's modulus, $Y=\frac{\text { Stress }}{\text { strain }}$

Strain $=\frac{\frac{F}{A}}{Y}$

Where,

Area, $A=\pi\left(R^{2}-r^{2}\right)=\pi\left((0.6)^{2}-(0.3)^{2}\right)$

Strain $=\frac{122500}{\pi\left[(0.6)^{2}-(0.3)^{2}\right] \times 2 \times 10^{11}}=7.22 \times 10^{-7}$

Hence, the compressional strain of each column is $7.22 \times 10^{-7}$

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