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Re: [Phys-l] History of MASS



On 10/19/2006 04:57 PM, David Abineri wrote:
I wonder if someone can comment on the historical development of the
concept of mass.

I'm still assuming this intends to ask about the distinction between
weight and inertia.

I am interested in both science and technology, so I find it amusing
to consider the history of weight/inertia _technology_, not just science.

Sometimes the technology greatly precedes the science, and sometimes
vice versa. We can discuss this in another thread if people are
interested.


A spectactular early example concerns John Harrison and his chronometers.
http://en.wikipedia.org/wiki/John_Harrison
He needed to build an oscillator (in this case a mass on a spring) in
such a way that it was highly insensitive to "frame forces" including
those due to acceleration, rotation, changing acceleration, changing
rotation, et cetera.

This makes contact with the recent "Good Questions" thread:

On 10/07/2006 06:26 PM, Cliff Parker wrote:>
.... Questions I can ask my
high school physics class that will cause them to apply things they have
learned over the years

Chronometer design is not something you can ask the class about
"cold turkey" but you can lead them through the issues. It is
IMHO a fine opportunity to "apply things they have learned". The
issues include:
-- Making an inertial platform with soft springs, shock absorbers,
and gimbals.
-- Making an oscillator such that "frame forces" act on it with
near-infinite mechanical disadvantage. This invites elegantly
symmetrical solutions. The "balance wheel" has inertia but
effectively no weight, i.e. no coupling to "frame forces".
-- Et cetera.