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From: james@umcp-cs.UUCP
Newsgroups: net.physics
Subject: Re: Hourglass Thought Experiment
Message-ID: <2924@umcp-cs.UUCP>
Date: Mon, 3-Oct-83 17:57:40 EDT
Article-I.D.: umcp-cs.2924
Posted: Mon Oct  3 17:57:40 1983
Date-Received: Wed, 5-Oct-83 09:06:02 EDT
References: <62@tekcad.UUCP>
Organization: Univ. of Maryland, Computer Science Dept.
Lines: 16

(Let us also have no friction, and no air inside the hourglass.)

Then, at any time, all mass in motion represents some kinetic energy,
which therefore must not contribute to the potential energy in the
compressed scale.  So the scale reading is effectively a function of
how much mass is in motion (and at what velocity.)  If we assume that,
between start and end, a constant amount of sand is always falling at
certain velocities, then the scale reading is constant, but less than
the 'real weight' of the hourglass+sand.  However, depending on the
shape of the hourglass, the motion of the sand which is slowly shifting
down towards the hole will vary with the amount of sand left in the upper
half of the hourglass, thus complicating everything.

Now can we invoke Einstein, Heisenberg, and Boltzmann?

  --Jim O'Toole