Drag force in a free fall

  • Thread starter skazis
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  • #1
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Main Question or Discussion Point

Hi,

An object is falling near the surface of the Earth. We assume there is a drag force acting on it due to the air molecules. It's initial conditions are such that it rotates and is in a chaotic motion.
Will the object will fall in the end in such a way to minimize air drag? And if yes - how can it be explained? I was thinking of least action principle as smaller drag force will make sure object reaches surface sooner.
 

Answers and Replies

  • #2
cjl
Science Advisor
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Nope - it may end up in a stable configuration (which is not necessarily, or even often, the least drag configuration), or it may continue tumbling. It mainly depends on the shape of the object and its mass distribution. Specifically, if the object has a relatively orientation-independent center of pressure, it will eventually end up with the center of mass below the center of pressure.
 
  • #3
DaveC426913
Gold Member
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Nope - it may end up in a stable configuration (which is not necessarily, or even often, the least drag configuration), or it may continue tumbling. It mainly depends on the shape of the object and its mass distribution. Specifically, if the object has a relatively orientation-independent center of pressure, it will eventually end up with the center of mass below the center of pressure.
A real world example: this happens often - and with lethal results - when jets flame out and go into a flat spin.

The flat spin is quite stable (the pilot is unable to escape from it), but at the same time is the highest drag configuration.
 

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