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[Phys-l] Fwd: Weight vs mass



I passed this question on to my friend in HOPOS, the history of the Phil of Science to see how they would respond. Here is the first response.

joe

Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556

Begin forwarded message:

From: Roger Anderton <R.J.Anderton@btinternet.com>
Date: October 20, 2006 2:58:31 PM EDT
To: HOPOS-L@listserv.nd.edu
Subject: Weight vs mass
Reply-To: Roger Anderton <R.J.Anderton@btinternet.com>

According to Robert DiSalle it was Newton that articulated there was a
difference between mass and weight:

"Against the background of this simple scheme, Newton's definitions have
some interesting features. Each one is the definition of some quantity, and
so it must explain how that quantity can be measured. E.g., "the quantity
of
matter is the measure of the same, arising from its density and bulk
conjointly." This seems intuitively fairly obvious: the quantity of matter
(i.e.mass) is "how much stuff" there is in a given volume. In the
background
of this definition, undoubtedly, is the Cartesian notion that matter is
reducible to extension (cf. Meditation III, Principles II); Newton is
making
it plain from the beginning that identical extensions can differ in a
fundamental physical property. We could think of this as a property
determinable by counting: a given volume contains some definite number n of
bits of matter, and a massive body differs from a less massive one by
containing more units of "stuff". In practice, however, such counting isn't
possible, and so we usually rely on weight to make the distinction. This is
one reason why the distinction between mass and weight was not clear before
Newton articulated it; apparently it was too obvious that weight provided a
simple means of distinguishing among equally extended bodies, one that
sufficed for most practical purposes. The fact that some bodies require
more
effort to lift seems to give a reasonably good measure of how much stuff
there is in a given volume, e.g. of how much grain there is in a vessel. "

http://instruct.uwo.ca/philosophy/470f/Newton3.html








----- Original Message -----
From: "jbellina" <jbellina@SAINTMARYS.EDU>
To: <HOPOS-L@listserv.nd.edu>
Sent: Friday, October 20, 2006 7:05 PM
Subject: Weight vs mass


A physicist on the physics list wonders what the led to the
distinction between mass and weight. I suggested it probably was
with Newton, but I'm sure someone(s) on this list can provide a more
complete answer. I will forward whatever reply to the physics list.

thanks,

joe

Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556