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'[OT]: -Air Drag (was: Botboard)'
2001\08\31@160346 by Ian Jordan

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I was always under the impression that air drag was the square of velocity,
and a search for "drag square velocity" on Google seems to return about
14,000 hits that agree.

Am I missing something?

> Air drag alone is KV^3.

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2001\08\31@184123 by Harold M Hallikainen

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       As I recall, force varies as the square of velocity. Power varies as the
cube of velocity. For example, double the speed and the force squares to
four times original. But, you're also now going twice as fast, so you go
twice the distance in the same amount of time. Energy used is force times
distance, so you've used eight times the energy in the same amount of
time (or eight times the power lost to drag).
       So, force varies as square, power varies as cube.

Harold

On Fri, 31 Aug 2001 13:06:02 -0700 Ian Jordan <spam_OUTianTakeThisOuTspamTWINGLES.COM> writes:
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2001\08\31@184958 by David VanHorn

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At 03:37 PM 8/31/01 -0700, Harold M Hallikainen wrote:
>         As I recall, force varies as the square of velocity. Power varies
> as the
>cube of velocity. For example, double the speed and the force squares to
>four times original. But, you're also now going twice as fast, so you go
>twice the distance in the same amount of time. Energy used is force times
>distance, so you've used eight times the energy in the same amount of
>time (or eight times the power lost to drag).
>         So, force varies as square, power varies as cube.


You're right, must be another senior moment.
At least the piano lessons are still... Awww #@$@#!%



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'[OT]: -Air Drag (was: Botboard)'
2001\09\01@080503 by Russell McMahon
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> I was always under the impression that air drag was the square of
velocity,
> and a search for "drag square velocity" on Google seems to return about
> 14,000 hits that agree.


The "traditional" drag formula, which give reasonable  results for subsonic
rockets, falling bowling balls,  skydivers and raindrops is

   Drag = 0.5 * Rho * Cd * A * V^2

Where Rho is fluid density
A is projected frontal area
Cd is drag coefficient
V = Velocity

In SI units:

For air at sealevel Rho is about 1.3 kg/m^3

Cd depends on frontal shape - use 1.0 for a flat plate, 0.3 is a super slick
low low drag design.

A in m^2, V in m/s

Drag in Newtons

Note that this formula is (as all are) a compromise solution which provides
reasonable results in many situations. Real drag calculations need rather
more than frontal area, density and velocity.



       RM

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2001\09\01@083644 by Jinx

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> Note that this formula is (as all are) a compromise solution
> which provides reasonable results in many situations. Real
> drag calculations need rather more than frontal area, density
> and velocity
>
>         RM

Did you see "Meet The Ancestors" this week Russell ? A
Neolithic arrow was reconstructed and sent to the UK Army
Ordnance Testing facility. According to their calculations
you'd have been lucky to get 60m with it. An actual bowman
got it to 148m with little trouble

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