Date: Thu, 17 Oct 2002 08:53:21 -0500

Author: "=?iso-8859-1?Q?Ram=F3n_O._Torres-Isea?="

Subject: RE: He balloon rising



Only while the buoyant force cancels exactly its weight...that is...if it
doesn't pop first.

Ramón O. Torres-Isea
Adjunct Lecturer and Supervisor,
Advanced Physics Laboratories.
Department of Physics,
The University of Michigan
at Ann Arbor, MI.

E-mail: rtorres@umich,edu
Phone: 734-764-3443

-----Original Message-----
[]On Behalf Of Anthony Lapinski
Sent: Thursday, October 17, 2002 6:47 AM
Subject: He balloon rising

A student asked me this the other day: If you let a He-filled balloon go,
it will rise. Will it rise at a steady rate (i.e., have an upward terminal
speed -- similar to a fealther falling downward)? I said probably not, and
there are many variables to deal with. As you go higher, gravity weakens,
air pressure decreases, and air temperature (in most parts) decreases in
our atmosphere. The student got me thinking about all of this. Would the
balloon have a constant upward speed near Earth's surface (i.e., assuming
gravity, pressure, and temperature were constant)?