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# Solve the following :

Question:

A stone is fastened to one end of a string and is whirled in a vertical circle of radius $\mathrm{R}$. Find the minimum speed the stone can have at the highest point of the circle.

Solution:

At highest point

$\mathrm{T}+\mathrm{mg}=\frac{m v^{2}}{R}$

For minimum speed, $\mathrm{T}=0$

$m g=\frac{m v^{2}}{R}$

$V=\sqrt{\mathrm{Rg}}$