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<DIV><FONT size=2>Hi Richard:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>You're confusing a lot of terms. Inertia is =
not a
quantifiable property of anything, it's an effect. It's not =
an
adjective, it's a noun. 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.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>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.
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.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>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.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Don A. Gilmore<BR>Mechanical Engineer<BR>Kansas
City</FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=Richard.Brekne@grieg.uib.no
href="mailto:Richard.Brekne@grieg.uib.no">Richard Brekne</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">Pianotech</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, December 20, =
2003 3:06
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Touchweight was =
Cockeyed
hammers / Don Gilmore</DIV>
<DIV><FONT size=2></FONT><BR></DIV>
<P>"Don A. Gilmore" wrote:
<BLOCKQUOTE TYPE="CITE"> <FONT size=-1>Hi =
Richard:</FONT> <FONT
size=-1>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.</FONT></BLOCKQUOTE>
<P><FONT size=2></FONT><BR>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.
<P>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..
<P>1. Inertia is no quantity at all. <BR>2. Inertia is equivalant to =
mass
<BR>3. Inertia is porportional to mass but porportional to velocity =
squared.
<P>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.
<P>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 <FONT =
color=#009900>(in terms
of finger work)</FONT> of mass and velocity <FONT =
color=#009900>(the
keystick)</FONT> required to accelerate another mass <FONT =
color=#009900>(the
whippen)</FONT> to a given velocity, so that it can in turn accelerate =
another
mass <FONT color=#009900>(the hammershank)</FONT> to yet another =
velocity.
Some of this pre-ordained by the leverage ratios of the key, whippen =
and
hammershank.
<P>So if using the term inertia is so problematic in this charge... =
lets not
use it... just describe this <<ideal>> in the relevant =
quantities
<P>-- <BR>Richard Brekne <BR>RPT, N.P.T.F. <BR>UiB, Bergen, Norway =
<BR><A
href="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> =
<BR><A
=
href="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broad=
park.no/~rbrekne/ricmain.html</A>
<BR><A
=
href="http://www.hf.uib.no/grieg/personer/cv_RB.html">http://www.hf.uib=
.no/grieg/personer/cv_RB.html</A>
<BR> </P></BLOCKQUOTE></BODY></HTML>