Size Reduction and Material Handling

A centrifugal discharge bucket elevator has a head pulley radius $R = 0.45\text{ m}$ (measured to the center of the bucket). Taking acceleration due to gravity $g = 9.81\text{ m/s}^2$, the critical rotational speed ($N_c$) in $\text{rpm}$ at which the centrifugal force balances gravity ($m \omega^2 R = m g$) is ________ (round off to 1 decimal place).