12246 IUPAC Gold Book - translational frictional coefficient 10.1351/goldbook.12246 12246 current synonym: frictional coefficient (in polymer science) 1 Frictional force, \(F\), per unit velocity, \(u\), experienced by an isolated spherical body moving unidirectionally in a viscous isotropic fluid, i.e., \(F = fu\). More generally, \(\boldsymbol{f}\) is defined as the tensor that correlates the vectorial frictional force, \(\boldsymbol{F}\), on a body in a viscous fluid and the vectorial velocity, \(\boldsymbol{u}\) , with \(\boldsymbol{F} = \boldsymbol{f}\boldsymbol{u}\). However, the more general definition is not needed in polymer science as experimental determinations of the translational frictional coefficient all employ situations in which \(\boldsymbol{F}\) and \(\boldsymbol{u}\) are collinear and \(F = fu\). \(f\) is related to the translational diffusion coefficient, \(D\), of an isolated body by the Einstein equation \(D = kT/f\), where \(k\) is the Boltzmann constant and \(T\) the thermodynamic temperature. translational diffusion coefficient https://goldbook.iupac.org//terms/view/12247 PAC, 2015, 87, 71. 'Definitions of terms relating to individual macromolecules, macromolecular assemblies, polymer solutions, and amorphous bulk polymers (IUPAC Recommendations 2014)' on page 97 (https://doi.org/10.1515/pac-2013-0201) https://goldbook.iupac.org/terms/view/12246/html https://goldbook.iupac.org/terms/view/12246/json https://goldbook.iupac.org/terms/view/12246/plain Citation: 'translational frictional coefficient' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.12246 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-06-13T16:04:59+00:00