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Name: June T.
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 7/14/2003


Question:
As a helium filled toy balloon ascends into the atmosphere, is the magnitude of its velocity constant or is the magnitude of its velocity increasing with altitude? Is the net lift force constant or increasing with altitude?


Replies:
June -

I would expect that the vertical velocity of the balloon would decrease with altitude. The buoyant force is a function of the difference between the density inside the balloon and that of the air outside the balloon. This difference would decrease as the balloon expands until at some altitude the two densities would be equal. At this altitude the balloon would cease rising.

It could also be the case that the balloon would expand to the point of bursting before the pressures would become equal. I believe this is the system used with the weather balloons. In this way, the radiosonde package drops back to earth.

The horizontal velocity of the balloon would generally increase with altitude and become more easterly. This is due to the prevailing winds at this latitude.

Larry Krengel



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