The paper by R. P. Feynman discusses the calculation of forces in molecular systems, emphasizing that forces can be calculated directly rather than indirectly through energy changes. This approach allows for an independent calculation of the slope of energy versus position curves, potentially increasing accuracy and reducing computational effort. The force on a nucleus in an atomic system is shown to be equivalent to the classical electrostatic force exerted by other nuclei and the electron charge distribution. The paper also explores different definitions of force in nonsteady and steady-state cases, proving that they are equivalent under steady-state conditions. The force on a nucleus is derived as the classical electrostatic attraction from all other nuclei and the electron charge density. The author highlights that strong attractive forces arise when there is a concentration of charge between two nuclei, leading to the formation of valence bonds. Additionally, van der Waals forces are interpreted as arising from charge distributions with higher concentrations between nuclei. The paper concludes with a discussion on the importance of intercrystalline thermal currents in the internal friction of polycrystalline metals, showing that these currents are dominant at small strains in annealed nonferromagnetic metals.The paper by R. P. Feynman discusses the calculation of forces in molecular systems, emphasizing that forces can be calculated directly rather than indirectly through energy changes. This approach allows for an independent calculation of the slope of energy versus position curves, potentially increasing accuracy and reducing computational effort. The force on a nucleus in an atomic system is shown to be equivalent to the classical electrostatic force exerted by other nuclei and the electron charge distribution. The paper also explores different definitions of force in nonsteady and steady-state cases, proving that they are equivalent under steady-state conditions. The force on a nucleus is derived as the classical electrostatic attraction from all other nuclei and the electron charge density. The author highlights that strong attractive forces arise when there is a concentration of charge between two nuclei, leading to the formation of valence bonds. Additionally, van der Waals forces are interpreted as arising from charge distributions with higher concentrations between nuclei. The paper concludes with a discussion on the importance of intercrystalline thermal currents in the internal friction of polycrystalline metals, showing that these currents are dominant at small strains in annealed nonferromagnetic metals.