Will a falling object minimize air drag?

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Discussion Overview

The discussion centers on the behavior of a falling object in the presence of air drag, particularly whether it will adopt a configuration that minimizes air resistance as it descends. The scope includes theoretical considerations of motion, drag forces, and stability in chaotic systems.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the object might fall in a way that minimizes air drag, referencing the least action principle to argue that reduced drag could lead to a quicker descent.
  • Another participant counters that the object may stabilize in a configuration that does not minimize drag, emphasizing that the outcome is influenced by the object's shape and mass distribution.
  • A similar point is reiterated, highlighting that a stable configuration, such as a flat spin, can result in high drag, using real-world examples like jets experiencing flat spins to illustrate this phenomenon.
  • A participant raises a question about the "flat penny" configuration, referencing an external article to explore whether it is indeed the most likely configuration during free fall.

Areas of Agreement / Disagreement

Participants express differing views on whether a falling object will minimize air drag, with no consensus reached. Some argue for the possibility of minimizing drag, while others assert that stable configurations may not align with this outcome.

Contextual Notes

The discussion reveals uncertainties regarding the influence of object shape and mass distribution on drag configurations, as well as the implications of chaotic motion on the final state of the falling object.

skazis
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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.
 
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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.
 
cjl said:
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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