- Revolutions per minute
**Revolutions per minute**(abbreviated**rpm**,**RPM**,**r/min**, or**r·min**) is a unit of^{−1}frequency : the number of full rotations completed in one minute around a fixed axis. It is most commonly used as a measure ofrotational speed orangular velocity of some mechanical component.Standards organization s 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

and we have::3600 r/min = 60 revolutions perhertz second = 60 HzIn the SI one often uses the unit for angular velocity which is

**radians per second**(**rad·s**)::1 r/min = 2π rad·min^{−1}^{−1}= 2π/60 rad·s^{−1}≈ 0.10471976 rad·s^{−1}To convert revolutions per minute to revolutions per second (hertz), one simply divides by 60. The opposite is true when converting from hertz to RPM, where one multiplies by 60 instead.

**Examples*** On some kinds of disc or tape-like recording media, the rotational speed of the medium under the read head is a standard given in r/min. Gramophone (phonograph) records, for example, typically rotate steadily at 16 2/3, 33⅓, 45 or 78 r/min (⁴⁄₁₅, ⁵⁄₉, ³⁄₄, or 1.3 Hz).

* Modern ultrasonicdental drill s can rotate at up to 800,000 r/min (10 kHz).

* The "second" hand of a conventional analogue clock rotates at 1 r/min.

* Audio CD players read their discs at a constant 150 kB/s and thus must vary the disc's rotational speed from around 500 r/min (actually 8 Hz), when reading at the innermost edge, to 200 r/min (actually 3.5 Hz) at the outer edge.cite web

url= http://www.mpeg.org/MPEG/DVD/Book_A/Specs.html

title= "Physical parameters of DVD"

accessdate= 2008-05-30

date= 1996-07-21

work= DVD Technical Notes

publisher= Moving Picture Experts Group (MPEG)] CD-ROM drives’ maximum rotational speeds are rated in multiples of this figure, even though they do not hold to constant read speeds when reading from most disc formats.

*DVD players also usually read discs at a constant linear rate. The disc's rotational speed varies from 1530 r/min (actually 25.5 Hz), when reading at the innermost edge, and 630 r/min (actually 10.5 Hz) at the outer edge. DVD drives’ speeds are usually given in multiples of this figure.

* Awashing machine 's drum may rotate at 500 to 2000 r/min (8–33 Hz) during the spin cycles.

* Anautomobile 'sengine typically varies between 700 and 7000 r/min (12–120 Hz) though some cars’ engines can spin as quickly as 11,000 r/min (180 Hz).

* A pistonaircraft engine typically rotates at a rate between 2000 and 3000 r/min (30–50 Hz).

* Computers’hard drive s typically rotate at 5400 or 7200 r/min (90 or 120 Hz)—most commonly with ATA or SATA interfaces—and some high-performance drives rotate at 10,000 or 15,000 r/min (160 or 250 Hz)—usually with SATA,SCSI orFibre Channel interfaces.

* The engine of aFormula One racing car can reach 19,000 r/min (320 Hz) under some circumstances. [*cite web|url=http://www.formula1.com/inside_f1/understanding_the_sport/5280.html|title=The Official Formula 1 Website|work=formula1.com|accessdate=2008-05-13*]

* AZippe-type centrifuge for enriching uranium spins at 90,000 r/min (1,500 Hz) or faster. [*cite web|url=http://www.electricityforum.com/news/mar04/centrifuge.html|title=Slender and Elegant, It Fuels the Bomb|work=electricityforum.com|accessdate=2006-09-24*]

*Gas turbine engines rotate at tens of thousands of r/min.JetCat model aircraft turbines are capable of over 100,000 r/min (1,700 Hz) with the fastest reaching 165,000 r/min (2,750 Hz). [*cite web|url=http://www.jetcatusa.com/p60.html| title=JetCat P-60 turbine specification page|work=jetcat.com|accessdate=2006-07-19*]* An

electromechanical battery (EMB) works at 60,000–200,000 r/min (1–3 kHz) range using a passively magnetic levitated flywheel in vacuum. [*Citation*] The choice of the flywheel material is not the most dense, but the one that pulverises the most safely, at surface speeds about 7 times the speed of sound.

last = Post

first = Richard F.

publication-date = April 1996

year = 1996

title = A New Look at an Old Idea: The Electromechanical Battery

periodical = Science & Technology Review

publication-place = Livermore, CA

publisher = University of California, Lawrence Livermore National Laboratory

pages = 12-19

id = ISSN: 10923055

url = http://www.llnl.gov/str/pdfs/04_96.2.pdf

accessdate = 2008-05-30*A

turbocharger can reach 290,000 r/min (4,800 Hz), while 80,000–200,000 r/min (1–3 kHz) is common.

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