Microbursts

wrote:

snip

For the physicists: what's the AVERAGE velocity of the nitrogen
molucules at 25 degree C & atmospheric pressure ?

From kinetic molecular theory of gases:

The *most probable* velocity (peak of the distribution)
c(p) = SQRT(2*k*T/m)

The average scalar velocity
c-bar = SQRT(8*k*T/pi*m)

The velocity of the molecule with average kinetic energy
SQRT(c^2-bar) = SQRT(3*k*T/m)

where k = Boltzmann's constant, T is absolute temperature, and m is
molecular mass.

Note that pressure is not a significant system variable in these
results - only temperature. Pressure *does* contribute to other
quantities such as collision frequencies and mean free path.

FWIW, c-bar for a nitrogen molecule at 25° C is about 1.31*10^5
cm/sec.

Tom Davidson
Richmond, VA

tadchem wrote:
wrote:

snip

For the physicists: what's the AVERAGE velocity of the nitrogen
molucules at 25 degree C & atmospheric pressure ?

From kinetic molecular theory of gases:

The *most probable* velocity (peak of the distribution)
c(p) = SQRT(2*k*T/m)

The average scalar velocity
c-bar = SQRT(8*k*T/pi*m)

The velocity of the molecule with average kinetic energy
SQRT(c^2-bar) = SQRT(3*k*T/m)

where k = Boltzmann's constant, T is absolute temperature, and m is
molecular mass.

Note that pressure is not a significant system variable in these
results - only temperature. Pressure *does* contribute to other
quantities such as collision frequencies and mean free path.

FWIW, c-bar for a nitrogen molecule at 25° C is about 1.31*10^5
cm/sec.

Oops! Make that 1.50*10^5 cm/sec


Tom Davidson
Richmond, VA

"tadchem" wrote in message
oups.com...

tadchem wrote:
wrote:

snip

For the physicists: what's the AVERAGE velocity of the nitrogen
molucules at 25 degree C & atmospheric pressure ?

From kinetic molecular theory of gases:

The *most probable* velocity (peak of the distribution)
c(p) = SQRT(2*k*T/m)

The average scalar velocity
c-bar = SQRT(8*k*T/pi*m)

The velocity of the molecule with average kinetic energy
SQRT(c^2-bar) = SQRT(3*k*T/m)

where k = Boltzmann's constant, T is absolute temperature, and m is
molecular mass.
...

Is this the point to jump in and argue that velocity is a vector quantity
and, therefore, the AVERAGE velocity is nearly zero? I would think that with
a little effort, it should be possible to spin this thread off into a
urinating contest about units or something like that.

:-)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

"tadchem" wrote
wrote:
"tadchem" wrote:

Well, this is interesting. Why are 9 and 10 day-old posts just
now showing up on google/deja? They seem to be duplicates?

BTW, this has been a really nice discussion - the first active
and useful one on this group for a year or more.

FloydR

Floyd Rogers wrote:
"tadchem" wrote
wrote:
"tadchem" wrote:

Well, this is interesting. Why are 9 and 10 day-old posts just
now showing up on google/deja? They seem to be duplicates?

I see them on Google in moments. Are you using Deja?

Tom Davidson
Richmond, VA