A stone tied to the end of a string of 1 m long is whirled in a horizontal circle with a constant speed. If the stone makes 22 revoluations in 44 seconds, what is the magnitude and direction of acceleration of the stone ?
${\pi ^2}\,$ m s$-$2 and direction along the radius towards the centre
${\pi ^2}\,$ m s$-$2 and direction along the radius away from the centre
${\pi ^2}\,$ m s$-$2 and direction along the tangent to the circle
${\pi ^2}\,$/4 ms$-$2 and direction along the radius towards the centre.
