Difference Between Similar Terms and Objects

Differences Between an RCF and an RPM


“RPM” stands for “rotations per minute” while “RCF” stands for “relative centrifugal force.”


RPM is an annotation by which a manufacturer of a rotating machine describes its rotational speed. In a linear motion, the speed of an object is measured in terms of meters per second or miles per hour. But in rotational motion, the speed of an object is denoted by its RPM. This speed in rotational motion is actually the frequency of the rotation. If the RPM of a rotating object is 200, then it means that the particular object is doing 200 revolutions per minute around a fixed axis.

This can also be understood with an example of computer disc. RPM is used to help determine the access time on computer hard disk drives. It is a measurement of how many complete revolutions a computer’s hard disk drive makes in a single minute. The higher the RPM, the faster the data will be accessed. For instance, if you were comparing 2 hard disk drives, 1 with 5,000 RPM and another with 7,500 RPM, the hard disk drive with a 7,500 RPM will be capable of accessing data much faster than the 5,000 RPM drive.

According to the SI (International System of Units), the RPM is not a unit. Rotations per minute is a measure of the “frequency” of the rotation whose SI unit is second-1 or per second.


Relative centrifugal force, or RCF, is measured in terms of gravity multiplied by force. This is also called the G-force. Centrifugal force represents the effect of inertia which arises in relation with the rotation, and it is experienced as an outward force away from the center of rotation. Relative centrifugal force, (RCF), describes the amount of force of acceleration applied to a sample in a centrifuge. The RCF is measured in multiples of or the number of times of the standard acceleration due to gravity at the Earth’s surface (x g). The RCF is described by two variables which are the radius and the angular velocity of the rotor. That is how wide the rotor is and how fast it is moving.

If the rotational speed is expressed in revolutions per minute (RPM) and the radius is given in centimeters (cm), then the RCF may be calculated through the following equation:

RCF = 1.1118 x 10-5  x  r x  N2


“r” stands for the radius of rotation in centimeters, and
“N” stands for the speed of the rotation measured in RPM.

RCF is an important parameter while calculating the effectiveness and efficiency of screens used in mining or the material handling industry. The higher the RCF of a screen, the higher will be its separation efficiency. Rotating devices such as centrifuges, centrifugal pumps, centrifugal governors, centrifugal clutches, etc. work on the concept of centrifugal force.


  1. “RPM” is “rotations per minute” while “RCF” is “relative centrifugal force.”
  2. RPM denotes the number of revolutions a rotating object is doing per minute while the RCF denotes the force applied on an object in a rotating environment.
  3. The RCF is calculated using the RPM and the radius.

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