<!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><style></style> Hi Richard: You're confusing a lot of terms.</blockquote> Well, I wont disagree with you there... but in my defense... grin... given the seemingly conflicting explainations... anybodies confusion on the matter shouldnt suprise at all.   <blockquote TYPE=CITE>Inertia is not a quantifiable property of anything, it's an effect.  It's not an adjective, it's a noun.</blockquote> Yes, you've more or less made that point, tho obviously there is some dissagreement about. <blockquote TYPE=CITE>You don't add or subtract inertia from anything.  It's just a scientific property.  I think what you are thinking of is just mass and moment of inertia.  Mass is the quality of an object that causes it to resist being accelerated.  Moment of inertia is the "rotational" equivalent of mass and is the quality of a rotating object that causes it to resist angular acceleration (speeding up or slowing down of rpm).  The moment of inertial is different from mass since it takes into acount the distribution of matter.  In other words, the more material that is further from the pivot point, the harder it is to accelerate (or decelerate) the object.  That's why flywheels have most of their mass toward the outer perimeter. Velocity is meaningless to inertia.  Only acceleration can produce/require a force.  Kinetic energy (mv^2 / 2) is simply a property of a moving object in terms of energy.  It has nothing really to do with inertia.  It is sort of a potential energy term and refers to how much energy the moving object could produce if you tried to stop it.</blockquote> .................. <blockquote TYPE=CITE>That's why we used it when the hammer struck the string.  The hammer, when moving, has usable energy.  To give it that energy we had to previously accelerate it to that speed.  To accelerate it requires force and that's where the properties of mass and moment of inertia come into play.  The more "massy" an object is, the more work you have to do and force you have to apply to accelerate it. There's no free lunch in physics.  X amount of work done by your finger is going to produce X amount of energy in the hammer no matter what the mechanism looks like.</blockquote> The first sentence is more or less what all this is about, and as much as you say there goes without saying. Dont you mean x amount of work will produce Y amount of energy ?... or are you really saying  5 units of work will produce 5 units of energy no matter whats inbetween?     <blockquote TYPE=CITE>Don A. Gilmore Mechanical Engineer Kansas City</blockquote> --     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>