Did you know... - (19/06)

At full power the Torrs Hydro New Mills turbine will spin at around 25 r.p.m.

Revolutions per minute (abbreviated rpm, RPM, r/min, or r·min−1) is a unit of frequency: the number of full rotations completed in one minute around a fixed axis. It is most commonly used as a measure of rotational speed or angular velocity of some mechanical component.

Standards organisations generally recommend the symbol r/min, which is more consistent with the general use of unit symbols. This is not enforced as an international standard; in French, for example, tr/mn (tours par minute) is commonly used.

The corresponding International System of Units (SI) unit would be the hertz and we have:
3600 r/min = 60 revolutions per second = 60 Hz

In the SI one often uses the unit for angular velocity which is radians per second (rad·s−1):
1 r/min = 2π rad·min−1 = 2π/60 rad·s−1 ≈ 0.10471976 rad·s−1

To convert revolutions per minute to revolutions per second (hertz), simply divide by 60.

Now don't you feel educated !