# A body of mass 1 kg is attached to one end of A wire and rotated in horizontal circle of diameter 40cm with a constant  speed of 2m/s what is the area of cross section of the witr if the stress developed in wire is 5×10^6N/m^2?

$\begin{array}{l} F=T=\frac{m v^{2}}{r}=\frac{1 \times 4}{0.2}=20 \mathrm{N} \\ \\ \text { Stress }=\frac{F}{A} \\ \therefore A=\frac{F}{\text { Stress }}=\frac{20}{5 \times 10^{6}} \\ \\ =4 \times 10^{-6} \mathrm{m}^{2}=4 \mathrm{mm}^{2} \end{array}$

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