revolution per second
FrequencyAngular speedexact by definition
The revolution per second is one full turn per second, numerically equal to one hertz. It is the rotational form of frequency, used where the thing being counted is a shaft turn rather than a waveform cycle, and it is the unit that makes shaft order analysis line up with a frequency spectrum.
Watch out: Equal to a hertz as a frequency, but not equal to a radian per second as an angular speed. One revolution per second is 2π rad/s, and confusing the two is the single most common error in rotational dynamics.
| 1 rev/s (Frequency) | 1 Hz |
| 1 rev/s (Angular speed) | 6.2831853 rad/s |
The revolution per second is exactly \(2\pi\) radians per second, about 6.2832 rad/s. It is a convenient unit for fast rotation where counting whole turns is natural, and it is numerically identical to the frequency in hertz of the rotation. The relation is exact by definition.