Mean free path
From Free net encyclopedia
In physics, in kinetic theory the mean free path of a particle, such as a molecule, is the average distance the particle travels between collisions with other particles. For sound waves in an enclosure, the mean free path is the average distance the wave travels between reflections off the enclosure's walls.
The formula for calculating the magnitude of the mean free path depends on the characteristics of the system the particle is in. For a particle with a high velocity relative to the velocities of an ensemble of identical particles with random locations, the following relationship applies:
- <math>\ell = (n\sigma)^{-1},</math>
Where <math>\ell</math> is the mean free path, n is the number of particles per unit volume, and σ is the effective cross-sectional area for collision. If, on the other hand, the velocities of the identical particles have a Maxwell distribution of velocities, the following relationship applies:
- <math>\ell = (\sqrt{2}\, n\sigma)^{-1}.\,</math>
External links
- Gas Dynamics Toolbox Calculate mean free path for mixtures of gases using VHS model