Audio CD players read their discs at a precise, constant rate (4.3218 Mbit/s of raw physical data for 1.4112 Mbit/s (176.4 KB/s) of usable audio data) and thus must vary the disc's rotational speed from 8 Hz (480 rpm) when reading at the innermost edge, to 3.5 Hz (210 rpm) at the outer edge.The second hand of a conventional analog clock rotates at 1 rpm.Modern air turbine dental drills can rotate at up to 800 000 rpm (13.3 kHz).Phonograph (gramophone) records, for example, typically rotate steadily at 16 + 2⁄ 3, 33 + 1⁄ 3, 45 rpm or 78 rpm (0.28, 0.55, 0.75, or 1.3, respectively, in Hz). On many kinds of disc recording media, the rotational speed of the medium under the read head is a standard given in rpm.A revolution is one complete period of motion, whether this be circular, reciprocating or some other periodic motion. For a wheel, a pump, or a crank shaft, the number of times that it completes one full cycle in one minute is given the unit revolution per minute.The conversions between a frequency f and an angular frequency ω are: Ī related but distinct quantity for describing rotation is angular frequency (or angular speed, the magnitude of angular velocity), for which the SI unit is the radian per second (rad/s).Īlthough they have the same dimensions (reciprocal time) and base unit (s −1), the hertz (Hz) and radians per second (rad/s) are special names used to express two different but proportional ISQ quantities: frequency and angular frequency, respectively. ISO 80000-3:2019 defines a physical quantity called rotation (or number of revolutions), dimensionless, whose instantaneous rate of change is called rotational frequency (or rate of rotation), with units of reciprocal seconds (s −1). Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min −1) is a unit of rotational speed (or rotational frequency) for rotating machines. JSTOR ( July 2016) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "Revolutions per minute" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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