Drag-velocity dependancy

1. Oct 24, 2007

TMM

I know that the drag force is proportional to the velocity to some power, n, and that n increases with velocity and with the viscosity of the medium.

I want to know why n increases, and how (mathematically) it increases. Some general speed ranges for v and v^2 in STP would be appreciated as well.

2. Oct 25, 2007

clem

n increases because turbulence increases.
The drag is so shape dependent, that I don't if there are formulas for n.
The fact that n depends on v means that n is really meaningless,
and is just used to make problems tractable

3. Oct 25, 2007

Stingray

This sort of thing is usually discussed by specifying how the drag coefficient varies with Reynolds number (which depends on velocity). You should find some nice plots if you search for those terms. Although these can be complicated, there are large regions where the drag coefficient remains approximately constant (F ~ v^2) or goes like 1/R (so F ~ v).

4. Oct 25, 2007

TMM

Alright, I looked up some things on Reynolds number as you suggested.

Thanks for the info.