Answer
$\omega=48.4\frac{rev}{min}$
Work Step by Step
We know that
$\omega=\sqrt{\frac{a_{cp}}{r}}$
We plug in the known values to obtain:
$\omega=\sqrt{\frac{5\times 9.81}{6.25ft\times 0.305\frac{m}{ft}}}$
$\omega=\frac{5.07}{s}\times \frac{1 rev}{2\pi rad}\times \frac{60s}{min}$
$\omega=48.4\frac{rev}{min}$