Date: Tue, 29 Jun 2004 14:34:54 -0400

Author: Wolfgang Rueckner

Subject: Re: Air resistance and falling objects


At 12:46 PM -0500 6/29/04, Cliff Bettis wrote:
>You can see the buoyant force of air acting on ordinary objects (filled with
>air or simply solid) if you weigh them on a balance and then repeat the
>weighing in a vacuum chamber. I like to use a small plastic pop bottle,
>emptied but with cap screwed on tightly. It clearly weighs more when you
>weigh it in a vacuum. For provoking thought, I unscrew the cap so that it is
>only loosely on and repeat the experiment.
>Cliff Bettis

It's not that the buoyant force doesn't come into play in Newton's
equation of motion, but rather that it's of secondary importance
because the density of air is so small relative to the densities of
"heavy" objects being dropped. The v^2 drag force is greater than
the buoyant force for these objects. -- Wolfgang
From Tue Jun 29 14:26:43 2004