Transport phenomena in ideal gases

On collision, each molecule performs a zigzag path. If one rectifies the molecnle s path one can assert that in the unit of time, the molecule describes the cylinder volnme with a height equal to the speed of the molecule o and with a cross-section ncP. The collision will take place with those molecules whose centers lie inside this cylinder. We shall consider that all molecules are at rest except those, which we follow up. Then the number of collisions in a unit of time v will make 

Consider the relation of the free path length X on the parameters of an ideal gas state. In an isothermal process p = nxT then X Up. So for nitrogen nnder normal conditions X = 10 m, at pressure 1 Pa 2 = 10 m, at pressure 10 Pa a molecule on average runs a long distance without collision (about 10 m). lfn = const., (isochoric process) X should 

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