Material Handling Equipment

In a centrifugal discharge bucket elevator, the critical speed of rotation $N_c$ (in rpm) at which centrifugal force equals gravitational force on a bucket of head pulley radius $r$ (in meters) is:

Options:

• (A) $N_c = \frac{60}{2 \pi} \sqrt{\frac{g}{r}} \approx \frac{29.9}{\sqrt{r}}$
• (B) $N_c = \frac{60}{\sqrt{g r}}$
• (C) $N_c = 2 \pi \sqrt{\frac{r}{g}}$
• (D) $N_c = \frac{g}{2 \pi r}$