What is meant by pressure being a momentum flux?

1. Jul 17, 2014

clumps tim

hi, I have been working on equation of state and one of my article says pressure is a momentum flux. what is the physical meaning of this? they have written it as

pressure =(1/3) *number density*volume*momentum

regards

2. Jul 20, 2014

Greg Bernhardt

I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?

3. Jul 21, 2014

clumps tim

no not yet, how is pressure a momentum flux?

4. Jul 21, 2014

Staff: Mentor

A flux of something has units of something per m2 per second: something / (m2·s).

So momentum flux would be (kg·m/s) / (m2·s). I'll let you simplify it.

Pressure is force per unit area: N/m2. Expand the newtons into basic units, simplify, and compare with the units of momentum flux.

5. Jul 21, 2014

A.T.

force is a momentum transfer rate:
momentum / time

pressure is force density :
force / area
or:
momentum / time / area

6. Jul 21, 2014

Staff: Mentor

Assuming that "number density" means something like "molecules per m3" and "momentum" means "momentum per molecule", the units are not consistent in this equation. I think "volume" should be "velocity", i.e. you have mis-interpreted a "v" in the original equation.

7. Jul 22, 2014

thank u all.