Revolutions per minute

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(Redirected from Rpm)

"Rpm" redirects here. For other uses, see Rpm (disambiguation).

For other uses, see Revolutions per minute (disambiguation).

Revolutions per minute (abbreviated rpm, RPM, r/min, or min⁻¹) is a unit of frequency, commonly used to measure rotational speed, in particular in the case of rotation around a fixed axis. It represents the number of full rotations something makes in one minute. The International System of Units (SI) unit for rotational velocity is the radian per second (rad·s⁻¹).

1 Examples
2 Symbols other than RPM
3 Compared to frequency and angular speed
4 See also
5 External links
6 References

[edit] Examples

Main article: Orders of magnitude (angular velocity)

The sweep of a second hand of an analogue clock or watch rotates at an average of 1 rpm.
Gramophone (phonograph) records typically rotate steadily at 16, 33⅓, 45 or 78 rpm.
Audio CD rotation rates vary from about 500 rpm when reading the innermost data track, to 180 rpm when reading tracks near the outer edge.
A washing machine's drum may rotate at 500 to 1800 rpm during the spin cycles.
An automobile's engine typically varies between 700 and 7000 rpm.
A piston aircraft engine typically rotates between 2000 and 3000 rpm.
A computer's hard drive rotates at 3600, 4200, 5400, or 7200 rpm on IDE types and 10 000 or 15 000 rpm on some SATA and SCSI and Fibre Channel drives.
A racing car engine's limit is close to 20 000 rpm in Formula One.^{[citation needed]}
A 52× CD-ROM drive can rotate a CD as fast as 10 350 rpm.
A Zippe-type centrifuge for enriching uranium spins at 90 000 rpm or faster.<ref>Slender and Elegant, It Fuels the Bomb. electricityforum.com. Retrieved on 2006-09-24.</ref>
Gas turbine engines rotate at tens of thousands of rpm. JetCat model aircraft turbines are capable of over 100 000 rpm with the fastest hitting 165 000 rpm.<ref>JetCat P-60 turbine specification page. jetcat.com. Retrieved on 2006-07-19.</ref>

[edit] Symbols other than RPM

Standards organizations generally recommend the symbol r/min, which better follows the general principles for forming unit symbols. But this is not enforced in fully metric countries as an international standard; for example, the French use the symbol tr/mn ('tours par minute').

[edit] Compared to frequency and angular speed

The International System of Units (SI) unit of frequency is the hertz (Hz):

1 r/min = 1/60 Hz

This is often used for measuring waves, such as radio and sound.

The SI unit of angular speed is the radian per second:

1 rev/min = 2π rad·min⁻¹ = 2π/60 rad·s⁻¹ = 0.10471976 rad·s⁻¹ online converter

However, there is no movement to use either of these units of measure (which are primarily used in physics) to replace revolutions per minute when measuring the rotational speed of machinery.