Material Handling and Storage

A bucket elevator has head pulley radius $r = 0.40\text{ m}$ (taking $g = 10\text{ m/s}^2$, so $g r = 4.0\text{ m}^2/\text{s}^2$). The critical belt speed $v_c = \sqrt{g r} = \sqrt{4.0}$ in m/s is: