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r.p.m. or gravity?

Gary Lum Gary.Lum at CASRDH.HEALTH.nt.gov.au
Wed Jan 28 17:16:37 EST 1998

Arturo Sanchez wrote:

> Can someone answer me the next question? How should I report the
> centrifugation speed r.p.m or gravity? Which one is correct? I have
> a discussion with a friend about this. I am reporting my methodology in
> r.p.m. but he says I should do it in g. I understand that r.p.m. are a
> unit of angular velocity equal to the uniform angular velocity of a body
> which rotates through an angle of 360° (2pi radians), so that every point
> in the body returns to its original point, in 1 minute. For me the key is
> in the "...uniform angular velocity". Am I right?

The report should be in relative centrifugal force (RCF), so in your
terms gravity (g).  The RCF varies as the radius length varies.  Two
centrifuges running at the same r.p.m. may be at different RCF.  You'll
find in scientific journals usually require you report in ...xg

There are nomograms available to determine the RCF from the radius and
r.p.m.  I also used to know the formula, but that was some time ago...



Dr Gary Lum
Director of Microbiology and Pathology
Royal Darwin Hospital

Microbiologists do it with culture and sensitivity
Meet me at http://www.ozemail.com.au/~glum/
Come and visit http://www.ozemail.com.au/~agar
E-mail me at mailto:glum at ozemail.com.au

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