Key Leads and Inertia

[Richard Brekne]

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Farrell wrote:

> Comments below: Terry Farrell > 1. Isnt this question about lead in
> the key really about its total mass, and
> > if you first were going to conceptually <<de-couple>> the lead mass
> and
> > dangle it on a string, wouldnt you have to do that for the wood mass
> as wellWell yes, but...... John is trying to demonstrate what the
> addition of lead to a key makes. The key with no lead with have
> certain inertia characteristics. The key with the lead will have
> different inertia characteristics. Comparing the force required to
> push the key down slowly (less than the acceleration due to gravity)
> with no lead and with the lead will reveal that less finger force is
> required when you have lead in the front portion of the key. Comparing
> no lead and lead when applying a forte blow (much greater acceleration
> than that due to gravity), it will require more force applied to the
> key with the lead to accelerate the key at the same rate as with no
> lead. Decoupling the lead in the diagram is simply to help visualize
> this phenomena.

Er,,,, grin.. All this is well and fine, and I dont think doesnt
understand that more mass means more force to accelerate it. Thats the
same with or without gravity. And seems to me we are forgetting whats on
the other side of the keystick in this. Something about this image
bothers me, and me thinks I have a bit of an itch behind my left ear
coming up :)

Answer me this then.... a see-saw with 5 grams of mass 1 meter from the
fulcrum on each side, and another with 500 grams of mass 1 meter on each
side of the fulcrum. Same scenerio.... less then 980/sec^2 acceleration
and then greater then that. While I'm pondering that on my evening
walk... I am sure ya'll will ponsk out an answer for me :)


>
> > 2. How fast is the approximate fastest we could expect the key to be
>
> > accelerated by human fingers in the first place ? Lift the front of
> the key up. Drop it. That is the acceleration due to gravity. A forte
> blow is many times (est.) the acceleration rate due to gravity.

I dont think that answers what I asked.


> > 3. Exceeding 980/sec^2 just means you are not getting any more
> <<help>> as
> > it were from the force that is gravity. But this isnt the same as
> saying
> > that doing so somehow creates an increase in resistance to
> > acceleration....yes ?? Its not like gravity has a kind of reverse
> gear
> > affect here. No, gravity does not change, it is an acceleration
> force that is consistent. The pianist is the one that is applying an
> additional acceleration force. If the finger force is less than that
> of gravity, adding lead to the key will decrease the amount of force
> required to push the key down at some acceleration rate less than that
> of gravity. If the finger force is greater than that of gravity,
> adding lead to the key will increase the amount of force required to
> push the key down at some acceleration rate greater than that of
> gravity.

Yes... something about this definantly bothers me..... grin... what else
is new eh ?  Well, I am off for a walk. Perhaps my mind will see more
clearly later on.

Cheers

RicB

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html


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