Date: Thu, 24 Oct 2002 11:30:44 -0500

Author: Paul Nord

Subject: Re: He balloon rising


Interesting. The y axis scale I understand. What is the horizontal
axis? It's labeled "MET (m)". Looks like meters to me. Hope you
didn't give any credit for a graph of feet vs. meters.


On Thursday, October 24, 2002, at 11:16 AM, Jerry DiMarco wrote:

> Here is an actual example to work with:
> jpg
> It is an altitude profile from a helium balloon experiment conducted by
> students recently. It looks fairly linear to me. The answer to your
> question is either simpler than we think or it is the case that some of
> the variables cancel each other out.
> The students are participating in a high altitude balloon flight
> program set up to give them the opportunity to design and conduct
> experiments and research projects. I became involved when they started
> borrowing equipment to test out their ideas. The high altitude photos
> have kept me interested. It is amazing how quickly (< 100,000 ft) the
> sky becomes black. Makes you realize how thin our atmosphere really
> is...
> Jerry
> At 05:47 AM10/17/2002, you wrote:
>> 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)?
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
> Jerry DiMarco
> Manager of Lecture Demonstrations and Instructional Labs
> Montana State Univ., Physics Dept.
> Bozeman, MT
> Our Motto: "We don't use anything the way it was meant to be used."