Revolutions Per Minute

Click Here for Items Related To - Revolutions Per Minute

Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min⁻¹) is the number of turns in one minute. It is a unit of rotational speed or the frequency of rotation around a fixed axis.

On many kinds of disc recording media, the rotational speed of the medium under the read head is a standard given in rpm. Phonograph (gramophone) records, for example, typically rotate steadily at 16 ²⁄₃, 33 ¹⁄₃, 45 or 78 rpm (0.28, 0.55, 0.75, or 1.3 Hz respectively).
Modern air turbine dental drills can rotate at up to 800,000 rpm (13.3 kHz).
The second hand of a conventional analogue clock rotates at 1 rpm.
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.^[1]
DVD players also usually read discs at a constant linear rate. The disc's rotational speed varies from 25.5 Hz (1530 rpm) when reading at the innermost edge, to 10.5 Hz (630 rpm) at the outer edge.^[1]
A washing machine's drum may rotate at 500 to 2,000 rpm (8–33 Hz) during the spin cycles.
A power generation turbine (with a two-pole alternator) rotates at 3000 rpm (50 Hz) or 3600 rpm (60 Hz), depending on country – see AC power plugs and sockets.
Modern automobile engines are typically operated around 2,000–3,000 rpm (33–50 Hz) when cruising, with a minimum (idle) speed around 750–900 rpm (12.5–15 Hz), and an upper limit anywhere from 4500 to 10,000 rpm (75–166 Hz) for a road car or nearly 20,000 rpm for racing engines such as those in Formula 1 cars (currently limited to 15,000 rpm).^[2] The exhaust note of V8 Thus a disc rotating at 60 rpm is said to be rotating at either 2 $π$ rad/s or 1 Hz, where the former measures the angular velocity and the latter reflects the number of revolutions per second.
If the non-SI unit rpm is considered a unit of frequency, then 1 rpm = 1/60 Hz. If it instead is considered a unit of angular velocity and the word "revolution" is considered to mean 2 $π$ radians, then 1 rpm = 2 $π$ /60 rad/s.

Examples

Examples (adsbygoogle = window.adsbygoogle || []).push({});

Examples