# The General Law of Fall of a Small Spherical Body through a Gas, and its Bearing upon the Nature of Molecular Reflection from Surfaces

@article{Millikan1923TheGL, title={The General Law of Fall of a Small Spherical Body through a Gas, and its Bearing upon the Nature of Molecular Reflection from Surfaces}, author={Robert Andrews Millikan}, journal={Physical Review}, year={1923}, volume={22}, pages={1-23} }

Law of fall of a small spherical body through a gas at any pressure.—(1) Theoretical derivation. When the ratio of free path to radius of droplet, l / a, is small, the resistance to motion is due entirely to viscosity and is proportional to a, while when l / a is large the resistance is due entirely to the inertia of the molecules hit and is proportional to a^2. The equation: F=6 pi eta av [1+A'l / a]-1 satisfies both these theoretical conditions. From Kinetic theory, however, it has been shown…

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