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Re: [Phys-l] Space Balloon




On Tue, 20 Feb 2007 14:43:18 +1100 thecraftyphantom@australia.edu writes:
Today as we were discussing gravitation and space, a student asked
the following:

On Earth a helium filled balloon rises because of bouyancy. How
would the same helium filled ballon move in a spacecraft (eg space
shuttle
cabin) if it was
a) in orbit around Earth
b) in "deep" space
I would be interested in how you would answer this question.
Peter Craft Corowa High School

*** a) If the spacecraft is in orbit around the earth, there must be a
downward force on the spacecraft to keep it in orbit. Remember that the
space shuttle cabin is usually filled with air at atmospheric pressure to
keep the astronauts happy. Since the helium filled balloon is lighter
than the air in the cabin, the air buoyancy force would lift it toward
the ceiling of the spacecraft.

b) In deep space, where the gravitational field is negligible,
gravitational forces disappear and everything, including the astronauts
and the helium balloon, would be freely suspended within the cabin.

Herb Gottlieb from New York City
(Where helium filled balloons rise toward the ceilings of our subways)