The drag exerted by the flow on a sphere is explicitly calculated by using the relation between the drag and a certain functional. A comparison of the results with the experimental data of Millikan gives excellent agreement.

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The Poiseuille flow of a rarefied gas in a tube of annular section is analyzed numerically for an inverse Knudsen number ranging from 0 to 10. The Bhatnagar-Gross-Krook model is used and the transport integro-differential equation is reduced to a purely integral one, which is solved numerically. The plot of the volume flow rate versus pressure is shown to have the expected minimum; it also fits rather well with experimental data.

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