Mean Free Path

Mean Free Path - Mean Free Path The motion of a molecule in...

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Mean Free Path The motion of a molecule in a gas is complicated. Besides colliding with the walls of the confinement vessel, the molecules collide with each other. A useful parameter to describe this motion is the mean free path λ . The mean free path λ is the average distance traversed by a molecule between collisions. The mean free path of a molecule is related to its size; the larger its size the shorter its mean free path. Suppose the gas molecules are spherical and have a diameter d. Two gas molecules will collide if their centers are separated by less than 2d. Suppose the average time between collisions is t. During this time, the molecule travels a distance v . t, and sweeps a volume equal to If on average it experiences one collision, the number of molecules in the volume V must be 1. If N is the number of molecules per unit volume, this means that or The time interval t defined in this manner is the mean time between collisions, and the mean free path λ is given by
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Mean Free Path - Mean Free Path The motion of a molecule in...

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