A boy ties a stone of mass 100 g to the end of a 2 m long string and whirls it around in a horizontal plane. The string can withstand the maximum…

A boy ties a stone of mass $\displaystyle 100$ g to the end of a $\displaystyle 2$ m long string and whirls it around in a horizontal plane. The string can withstand the maximum tension of $\displaystyle 80$ N. If the maximum speed with which the stone can revolve is $\displaystyle \frac{\mathrm{K}}{\pi} \mathrm{rev} . / \mathrm{min}$. The value of K is : (Assume the string is massless and unstretchable)