THEORY OF FRICTION - COULOMB DRAG BETWEEN 2 CLOSELY SPACED SOLIDS

We calculate the friction force between two metallic bodies with hat s urfaces separated by a vacuum slab of thickness d, and moving with a r elative velocity upsilon. The separation d is assumed to be so large t hat the only interaction between the bodies is via the Coulomb field. The friction force depends linearly on the velocity upsilon (for small upsilon) and decays rapidly with increasing d. In most practical case s, the Coulomb drag makes a negligible contribution to the friction fo rce, but it may make an important contribution in some special cases.