Frictional coefficient of sphere

Perrin in 1936 derived equations that relate frictional coefficients to the shape of macromolecules formed as ellipsoids of revolution. The frictional coefficients (/) of prolate and oblate ellipsoids (see Chapter 8) are both greater than the frictional coefficients of spheres (/( or /o) of equal volume. The difference depends on the ratio of the major to the minor axis. Let p = b/a be the axial ratio, where b is the equatorial radius and a is the semiaxis of revolution. For prolate ellipsoids or elongated ellipsoids a/b > 1), we have... 

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