Re: [Phys-L] Dirigible Flight Question

[Bernard Cleyet <bernardcleyet@redshift.com>]

On 2012, Nov 05, , at 15:11, Paul Nord wrote:

> Ok, ok.  I'll give you the real question.  We've gotten bogged down in dirigibles and blimps.
>
> I have altitude data for a weather balloon which picks up enough ice at a 5 km altitude that it begins to descend.  It continues dropping until it reaches about 2 km where enough ice has melted to allow the balloon to continue its ascent.  We know the lift of the balloon.  We know the mass of the payload.  What is the mass at the two points where the velocity goes to zero?
>
> Paul


This is similar, I pray, to the oscillating party balloon AJP article discussed.    In that case the ice is the string hanging from the balloon.



The intriguing midair oscillations of a party balloon, which occur once its buoyancy is no longer
capable of keeping it against the ceiling, is shown to require a rather sophisticated explanation in
terms of variable-mass dynamics. The ubiquity of this phenomenon, the accessibility of its actual
observation, and the subtlety of its analytic description provide a good opportunity for an interesting
zero-cost classroom demonstration. © 2007 American Association of Physics Teachers.
DOI: 10.1119/1.2733684


https://docs.google.com/viewer?a=v&q=cache:I_OscjM_aXkJ:authors.library.caltech.edu/13243/1/YARajp07.pdf+oscillating+toy+balloon&hl=en&gl=us&pid=bl&srcid=ADGEESjG4N2zBYdRa38Cfa3PdeA9afE-hILcNyokUIcXc5uzra2UTiqtAmDSZFwd8veOXwYza2Vl6UeYbp_V0jj-l4O7Lx43qDF43CRMvBOfwXHpd3385mBjvNfYlJMzq3UQ7b8ng6pJ&sig=AHIEtbS8GV5nbCeOEVcc2wHj5cTR_s52cg

Of course, you've the added prob. of the variable buoyancy due to the variable ambient pressure, and, therefore, the variable volume of the balloon!


Tough!

bc was searching for the damping of an oscillating blimp; thinking Q < 5, not the minutes to decay as claimed by JC