Drag time of terminal velocity?

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Discussion Overview

The discussion revolves around understanding the time and speed of an object as it approaches terminal velocity, particularly focusing on the effects of air resistance and the conditions under which this occurs. The scope includes theoretical considerations and mathematical modeling related to motion in a gravitational field.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about how to determine the time and speed of an object before it reaches terminal velocity, noting that acceleration decreases.
  • Another participant suggests that solving the differential equation governing the motion reveals that the object never truly reaches terminal velocity, but can approach it asymptotically, allowing for calculations of time to reach certain percentages of terminal velocity.
  • A third participant mentions that for a one-dimensional case with uniform gravitational field and air resistance, an integral can be solved, referencing a Wikipedia article for further details.
  • Another viewpoint proposes that for a perfect sphere, it may be possible to estimate the time and speed more accurately, while noting that other shapes may experience changes in terminal velocity due to wobbling during descent.

Areas of Agreement / Disagreement

Participants express differing views on the nature of reaching terminal velocity, with some emphasizing the asymptotic approach and others discussing the impact of object shape on terminal velocity. No consensus is reached on the exact methods or implications of these points.

Contextual Notes

Limitations include the assumptions made about the shape of the object and the uniformity of the gravitational field, as well as the unresolved mathematical steps involved in the differential equations discussed.

Isawyou0
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Hi all!
How can we know the time and speed of the object before it reachs the terminal veocity, it will reach that, but when?
(he's acceleration decreseases right) thanx
 
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If you solve the usual differential equation, the object will never reach the terminal velocity exactly. You can give the time needed until the object reaches 50%, 90%, 99%, ... of the terminal velocity. That will come out of the solution of the differential equation.

If you are just interested in the rough timescale, calculate how long an object without air resistance needs to reach the terminal velocity of the object with resistance.
 
You could probably get really close as to when and how fast if you're looking at a perfect sphere. Everything else wobbles when it falls, thus it's terminal velocity changes with time.
 

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