Rule. Multiply one-half the weight of the disc by the height due to the velocity of its circumference in feet per second.

Example

A grind-stone 3 3/8 feet in diameter, weighing 2000 lbs., is required to make 362¼ revolutions per minute; what power must be communicated to it ?

Circum. of 3 3/8 =10.6 feet, which X 362.25 and / 60 = 64 feet per second. Then 2000 / 2 X 64 = 64000 lbs. raised 1 foot.

Note

If the reolving disc is not an entire or solid wheel, being a ring or annulus, it most first be computed as if an entire disc, and then the portion wanting must be computed and deducted.