What is meant by pressure being a momentum flux?

[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

please explain me the expression

regards

 

[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?

 

[clumps tim]

no not yet, how is pressure a momentum flux?

 

[jtbell]

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.

 

[A.T.]

no not yet, how is pressure a momentum flux?

force is a momentum transfer rate:
momentum / time

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

 

[jtbell]

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

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.

 

[clumps tim]

thank u all.