A stone tied to the end of string of 80 cm long, is whirled in a horizontal circle with a constant speed. If the stone makes 25 revolutions in 14 s. Then magnitude of acceleration of the same will be

If angular velocity is $\omega$ and radius of circular path is r then, acceleration $\alpha = {\omega }^{2}r$

where $\omega = \frac{2\mathrm{\pi }}{T}$

$T = \frac{Number of revolutions}{Time taken} = \frac{25}{14} = 1.78 s$

$and \omega = \frac{2\mathrm{\pi }}{1.78} = 3.52 rad/s$

Hence, $\alpha = {(3.52)}^2\times 80 = 991.23 = 990$$cm/s^2$