repulsion

Repulsion is a force or tendency that drives bodies or systems apart. In physics, repulsion occurs between like charges or like magnetic poles; opposite charges attract, like charges repel. The magnitude of the electric repulsion follows Coulomb's law: F = k|q1 q2|/r^2, directed away from each other. Magnetic repulsion arises when two magnets with the same pole face each other, producing a force that pushes them apart.

In quantum chemistry and atomic physics, electrons experience repulsion through Coulomb forces. When electrons occupy the same region of space, exchange and correlation effects contribute to additional repulsive interactions. In molecular modeling, short-range repulsion is often represented by a repulsive term in the potential, such as the Lennard-Jones potential, which scales as r^-12 at small separations to prevent particle overlap.

In materials science, repulsion between atoms at close approach prevents nuclei from occupying the same space and helps determine bond lengths and lattice spacings. Repulsive interactions balance attractive forces to establish stable structures, including crystals and molecular frameworks, and they influence mechanical properties and phase behavior.

In social and psychological contexts, repulsion denotes aversion or hostility that motivates avoidance or distancing between individuals or groups, often arising from perceived threat, incompatibility, or conflicting interests.

In cosmology, discussions sometimes describe a form of repulsion related to the universe’s accelerated expansion, typically attributed to dark energy or a negative pressure component, rather than a conventional force between particles.