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.
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 $7.22 \times 10^{-7}$
A wire of length $L$ and radius $r$ is clamped at one end. If its other end is pulled by a force $F$, its length increases by $l$. If the radius of the wire and the applied force both are reduced to half of their original values keeping original length constant, the increase in length will become.
The area of a cross-section of steel wire is $0.1\,\,cm^2$ and Young's modulus of steel is $2\,\times \,10^{11}\,\,N\,\,m^{-2}.$ The force required to stretch by $0.1\%$ of its length is ......... $N$.
On all the six surfaces of a unit cube, equal tensile force of $F$ is applied. The increase in length of each side will be ($Y =$ Young's modulus, $\sigma $= Poission's ratio)
Young's modulus is determined by the equation given by $\mathrm{Y}=49000 \frac{\mathrm{m}}{\ell} \frac{\text { dyne }}{\mathrm{cm}^2}$ where $\mathrm{M}$ is the mass and $\ell$ is the extension of wre used in the experiment. Now error in Young modules $(\mathrm{Y})$ is estimated by taking data from $M-\ell$ plot in graph paper. The smallest scale divisions are $5 \mathrm{~g}$ and $0.02$ $\mathrm{cm}$ along load axis and extension axis respectively. If the value of $M$ and $\ell$ are $500 \mathrm{~g}$ and $2 \mathrm{~cm}$ respectively then percentage error of $\mathrm{Y}$ is :
A wire extends by $1 mm$ when a force is applied. Double the force is applied to another wire of same material and length but half the radius of cross-section. The elongation of the wire in mm will be ........