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A centrifuge is a piece of equipment, generally driven by a motor, that puts an object in Rotation Around A Fixed Axis , applying force perpendicular to the axis. The centrifuge works using the Sedimentation Principle , where the Centripetal Acceleration is used to separate substances of greater and lesser density. There are many different kinds of centrifuges, including those for very specialised purposes. THEORY Protocols for centrifugation typically specify the amount of Acceleration to be applied to the sample, rather than specifying a Rotational Speed such as Revolutions Per Minute . The acceleration is often quoted in multiples of g, the acceleration due to Gravity at the Earth's surface. This distinction is important because two rotors with different diameters running at the same rotational speed will subject samples to different accelerations. The acceleration can be calculated as the product of the Radius and the square of the Angular Velocity . HISTORY AND PREDECESSORS English military engineer Laval (1707-1751) invented a whirling arm apparatus to determine Drag , and Antonin Prandl invented the first centrifuge in order to separate cream from milk to make churning butter much easier. TYPES AND USES There are basically four types of centrifuge:
Laboratory centrifuge See Also: Laboratory centrifuge Simple centrifuges are used in chemistry, biology, and biochemistry for isolating and separating suspensions. They vary widely in speed and capacity. They usually comprise a rotor containing two, four, six, or many more numbered wells within which the samples contained centrifuge tips may be placed. Isotope separation Other centrifuges, the first being the Zippe-type Centrifuge , separate Isotope s, and these kinds of centrifuges are in use in Nuclear Power and Nuclear Weapon programs. Gas Centrifuge s are used in Uranium Enrichment . The heavier Isotope of uranium ( Uranium-238 ) in the Uranium Hexafluoride gas tend to concentrate at the walls of the centrifuge as it spins, while the desired Uranium-235 isotope is extracted and concentrated with a scoop selectively placed inside the centrifuge. It takes many thousands of centrifuges to enrich uranium enough for use in a Nuclear Reactor (around 3.5% enrichment), and many thousands more to enrich it to atomic bomb-grade (around 90% enrichment). ]] Aeronautics and astronautics Human Centrifuges are exceptionally large centrifuges test the reactions and tolerance of Pilots and Astronaut s to acceleration above those experienced in the Earth's Gravity . The US Air Force at Holloman Air Force Base , NM operates a human centrifuge. The centrifuge at Holloman AFB is operated by the Aerospace Physiology department for the purpose of training and evaluating prospective fighter pilots for high-g flight in Air Force fighter aircraft. It is important to note that the centrifuge at Holloman AFB is unrealistic in that it is far more difficult for a pilot to tolerate the high-g environment in the centrifuge than in a real fighter aircraft. This well-known fact is based on countless accounts from experienced operational fighter pilots. The use of large centrifuges to simulate a feeling of gravity has been proposed for future long-duration space missions. Exposure to this simulated gravity would prevent or reduce the . Commercial applications
CALCULATING RELATIVE CENTRIFUGAL FORCE (RCF) Relative centrifugal force is the measurement of the force applied to a sample within a centrifuge. This can be calculated from the speed (RPM) and the rotational radius (cm) using the following calculation. : where g r N SEE ALSO EXTERNAL LINKS
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