revolutions per minute
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 organizations 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 = 2p rad·min−1 = 2p/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, 33?, 45 or 78 r/min (4/15, 5/9, ³/4, or 1.3 Hz).
Modern ultrasonic dental drills 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.
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.
A washing machine's drum may rotate at 500 to 2000 r/min (8–33 Hz) during the spin cycles.
An automobile's engine 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 piston aircraft engine typically rotates at a rate between 2000 and 3000 r/min (30–50 Hz).
Computers’ hard drives 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 or Fibre Channel interfaces.
The engine of a Formula One racing car can reach 19,000 r/min (320 Hz) under some circumstances.
A Zippe-type centrifuge for enriching uranium spins at 90,000 r/min (1,500 Hz) or faster.
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).
An electromechanical battery (EMB) works at 60,000–200,000 r/min (1–3 kHz) range using a passively magnetic levitated flywheel in vacuum.
A turbocharger can reach 290,000 r/min (4,800 Hz), while 80,000–200,000 r/min (1–3 kHz) is common.
See also
Orders of magnitude (angular velocity)
Constant linear velocity, or CLV, used when referring to the speed of audio CDs
Constant angular velocity, or CAV, used when referring to the speed of gramophone (phonograph) records
Turn (geometry)
References
|
|
|
|
This section is sponsored by:
Looking for Revolutions Per Minute?
Find it NOW on NeXplore.com! The New Web 2.0 Search Engine!
www.nexplore.com
Limited Offer
How About Take 3 Seconds to Enter Postal Address to Claim Your Free Laptop Now while you are looking for Revolutions Per Minute?
www.RewardLaptop.com
Laptops
Find a great deal on a Laptop Computer by browsing our Laptop Computer listings.
www.LaptopComputersInfo.com
laptops
Don't just search for laptops, find results.
www.ask.com
Top Laptops Info. All in One.
Find great deals and info on Laptops. Search smart for the right stuff with OXY.
www.oxysearch.com
Extreme Laptop Sale
Ultra Performance Notebook Systems Save up to $2000 on special units!
www.notebookchoice.com
Laptop
Laptop At Huge Discount! Free Shipping On Laptop.
www.insights1.com
Best Rated Laptops
Looking To Buy A Laptop? Which Are The Best Laptop Brands?
BestRatedLaptops.info
|
