# RMS velocity of air

1. Jul 5, 2008

### cyclonefb3

1. The problem statement, all variables and given/known data
If the air pressure is 72 cm-Hg (as measured with a barometer), the velocity of sound is 344.7013 m/s and the temperature is 22.6 C calculate the Vrms.

2. Relevant equations

velocity = Vrms*sqrt[(1.40*n*Na*m)/(3*density*Vol)]

3. The attempt at a solution

I am under the impression that the Nam cancels out the density*volume, but I'm not getting the right answer. I'm really having trouble assigning values for all the parts of the equation.

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jul 5, 2008

### Redbelly98

Staff Emeritus
If the quantities are what I think they are***, then n*Na*m would cancel density*volume. This will leave an equation with two quantities, "velocity" and "Vrms". I know what Vrms is, but have know idea what "velocity" refers to in this equation.

Hint: can you find a different equation in your textbook, one that involves both Vrms and Temperature?

*** p.s. correct me if I'm wrong, but I believe that:
n is the number of moles of air molecules
Na is Avagadro's number, 6.02 x 10^23
m is the mass of a single molecule.