<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> <body bgcolor="#FFFFFF" style="FONT-SIZE: 14pt; FONT-FAMILY: Arial; BACKGROUND-COLOR: #ffffff">   "Don A. Gilmore" wrote: <blockquote TYPE=CITE> Hi Richard: I'm not sure what the qualifications of your "physics guy" are, but inertia is not even an engineering quantity.  There are no units of "inertia".  It is just a concept regarding the nature of matter.  All bodies with mass have inertia and tend to want to stay at a constant velocity and move in a straight line.</blockquote> Been thinking about this statement Don. No units of inertia. Fair enough... but a thing does have inertia, and in some sense it has to be measureable or calculable .... or else the concept is really meaningless.  Say you have a 20 kilo ball and you want to accelerate it from 0 to 10 m/sec. Whatever way you want to describe the work needed to do this has to somehow deal with the exact amount of inertia this ball has. If this wasnt true... then how could one speak of one thing having more or less inertia then another. Ok... so inertia according to you doesnt have a number per se... as far as I can see that makes three "definitions" of inertia by physics experts on the list here.. 1. Inertia is no quantity at all. 2. Inertia is equivalant to mass 3. Inertia is porportional to mass but porportional to velocity squared. Now honestly guys.... how are we to deal with how much or what range of inertia in the key is desirable for a given ratio and a give top action inertia... when we seemingly cant even agree on what inertia is. The term is used all the time to describe the amount of difficulty there is in changing the velocity of a thing. Whatever the term... we need to be able to find some <<ideal>> combination (in terms of finger work)  of mass and velocity (the keystick) required to accelerate another mass (the whippen) to a given velocity, so that it can in turn accelerate another mass (the hammershank) to yet another velocity. Some of this pre-ordained by the leverage ratios of the key, whippen and hammershank. So if using the term inertia is so problematic in this charge... lets not use it... just describe this <<ideal>> in the relevant quantities -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway <A HREF="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> <A HREF="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A> <A HREF="http://www.hf.uib.no/grieg/personer/cv_RB.html">http://www.hf.uib.no/grieg/personer/cv_RB.html</A>   </body> </html>