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Re: balances



It is something John Poynting would have been familiar with.
He used a chemical beam balance in the vertical gradient mode,
rather than Lord Cavendish's Michell (horizontal) torsion balance.

Where there is a gross g gradient, the vertical asymmetry
of the masses of the beam balance can provide varying indication.

A more practical instance might spring from consideration of
the source of the variation of g from 9.78 to 9.83 from
place to place. Masscons apart, the variability correlates
with latitude, of course.

So if we carry our faithful beam balance onto a turn table
- or roundabout if you will, we might expect to see an equivalent
gradient affecting the lower pendulous sample mass, than the upper
beam center of gravity.

The effect is very, very small, so we might need to spin the turn table
rather fast. But then, that's the essence of a nit-pick: small
but annoying? :-)

Brian

At 20:35 9/27/01 -0700, you wrote:
brian

Pray tell; write off list if you wish.

Panzers,

bc

Non vertically directed acceleration????


brian whatcott wrote:

At 16:40 9/27/01 -0600, you wrote:
PHYS-L@lists.nau.edu writes:
I prattle that though beam balances measure mass:


Okay I am confused, maybe. Here is what I think:

An equal arm or pan balance must have either a gravity field or
accelerated reference frame in order to work. They will be calibrated in
mass units as both sides have the same "g-factor" and the torques balance.
/snip/
What am I missing?

Thanks

Ken Fox

Hehehe...I thought of a couple of ways that a chemical beam balance
would provide a varying reading of the value of a milligram weight on
one pan, depending on the accelerated reference frame in question.

But perhaps I should let it sit for a while.

Brian

brian whatcott <inet@intellisys.net> Altus OK
Eureka!