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Re: apparent weight



On Sat, 14 Feb 1998, LUDWIK KOWALSKI wrote:

You forgot to specify, (I am not criticizing you for this) that the
acceleration is "in our so-called inertial frame of reference". Some
want to make a central issues out of it, others prefer to focus on
differences between v and a, or between mass and weight. Unfortunately,
many students have difficulties with these things. That is the issue.

I'm not quite sure what you mean when you say "in *our* ... inertial frame
of reference." I prefer to measure accelerations relative to *any* local
inertial (i.e., "freely falling") frame and to call the opposite of that
acceleration the local gravitational field strength in *my* frame of
reference.

Some said we need a new noun, microgravity, others said that the one
we already use, apparent weight, is good enough for the purpose of
dealing with a specific activity in a specific elevator using a specific
forcemeter.

Because I haven't heard anyone explicitly correct the misconception that
"microgravity" is just a weak "gravitational force" or that it is somehow
related to "apparent weight" allow me to do so: "Microgravity" refers to
the tidal effects which are gravity's only essential contribution to the
observable world and which are exceedingly small (hence, "micro") near the
earth. In a freely falling frame like the shuttle--which eliminates the
overwhelming and misleading appearance of a nearly uniform "gravitational
field"-- we find it much easier to observe these tidal effects.

John
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A. John Mallinckrodt http://www.intranet.csupomona.edu/~ajm
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