Re: timing data for falling objects

[Brian Whatcott <betwys@DIRECTVINTERNET.COM>]

At 10:04 AM 7/7/02, Michael Bowen, you wrote:


> [Hugh Haskell]
> >... [Y]ou can see that the drag force law scales
> > as the cross-sectional area, with only a small
> > dependence on the shape and the material.
> >That's worth seeing.
>
> Drag force or drag coefficient? I have a vague recollection of the drag
> force as having a fairly specific velocity dependence.
>
> I'm also curious about the experimental and computational details,
> especially those that allow one to compute the drag coefficient from data
> taken in a typical classroom setting without making _ad hoc_ assumptions,
> and without using a wind tunnel.
>
> If this can be pulled off under the stated conditions, I have to agree that
> it would be worth seeing.
>
> --MB


It is conventional to express a force due to air drag as
Fd = Cd . A . 1/2 rho V^2
where Cd is a coefficient expressing a shape and texture
  at a reasonable range of sizes and speeds

A is a representative area
rho is a density
V is the air speed    .....in any consistent system of units.

The Cd is the carpet under which all the variabilities seen in experimental
situations  are swept.


Brian Whatcott
  Altus OK                      Eureka!