2002-07-17 The problem with rev/s is that it isn't universal. In German, it is U/s. Hertz, is universal and thus would be the proper choice. Plus, I'm sure Americans would argue to keep the minute as a time base and continue to use RPM.
There is another unit in SI that is also equal to the reciprocal second, and that is the bequerel (Bq), It is loosely defined as the number of random nuclear degeneration's per second. Whereas hertz is based on "repeating cycles", the bequerel is based on random nuclear events. John ----- Original Message ----- From: "Gene Mechtly" <[EMAIL PROTECTED]> To: "U.S. Metric Association" <[EMAIL PROTECTED]> Cc: "U.S. Metric Association" <[EMAIL PROTECTED]> Sent: Wednesday, 2002-07-17 20:16 Subject: [USMA:21204] What can we replace rpm with? > Carter, > > By the rowlett definition, Hz is restricted to a "periodic" cycle (with > a (at least implied) fixed frequency of rotation. > > In many cases of rotating shafts, the rate of rotation is a variable, > not periodic. In these cases, the rowlett definition must be rejected. > > In contrast, the BIPM Brochure does not require cycles measured by the > Hz to be constant. Thus, the Hz is acceptable for a variable rate of > shaft rotation, but I would prefer rev/s for simple cases of rotating > shafts, or rad/s for more complicated cases of rotations where the > calculus and differential equations are the appropriate tools. For > example, analysis of a rigid body "tumbling" about all three axes. > > Gene. > ......................................... > On Wed, 17 Jul 2002, Carter, Baron wrote: > > > If we accept the following definition of Hz (from > > http://www.unc.edu/~rowlett/units/dictH.html) then surely Hz would be the > > obvious choice in replacing rpm? > > > > "the SI unit of frequency, equal to one cycle per second. The hertz is used > > to measure the rates of events that happen periodically in a fixed and > > definite cycle; .............." >
