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Re: Weight and Mass



At 04:58 PM 9/27/01 -0500, brian whatcott conjectured:
... that though beam balances measure mass:
the pointer reading is still g dependent, like a spring scale.

Does anybody have any experimental and/or theoretical support for this
conjecture?

There seems to be overwhelming theoretical evidence to the contrary.

One form of the theoretical argument appeals to linearity and
superposition, as follows:

There will be some part of the beam-balance that represents "down". This
will be determined by the center of mass relative to the position of the
pivot. The calculation of center of mass is independent of g. If we
increase the magnitude of g, down is still down, only more so. The
configuration of the pointer should be unaffected. This assumes of course
an ideal non-deforming springless beam-balance.

There are probably other arguments that lead to the same conclusion.

There is also some suggestive experimental evidence: Highly-accurate
laboratory balances have no provision for calibration, except in the Nth
decimal place, whereas we know that g varies significantly from location to
location.