Attractionrepulsion

Attractionrepulsion is a general term used to describe physical interactions that can cause entities to move toward each other (attraction) or away from each other (repulsion) depending on their properties and the governing forces. It encompasses both universally attractive forces and those that can reverse sign with distance, charge, orientation, or other conditions.

The best known examples are gravity, which is always attractive between masses, and electromagnetic forces, which can be either attractive or repulsive depending on charge signs. Magnetic and nuclear forces add further complexity, with short-range repulsion often arising from quantum mechanical effects and electron cloud overlap, and longer-range attraction from bonding or van der Waals interactions.

Mathematical descriptions separate attractive and repulsive contributions. For point charges, Coulomb's law F = k q1 q2 / r^2 yields an attractive force for opposite charges and a repulsive force for like charges. In molecular physics, potentials such as the Lennard-Jones form include a short-range repulsive term and a longer-range attractive term, modeling how particles approach and bind.

The balance of attraction and repulsion determines structure and stability in systems from gases and liquids to solids, colloids, and plasmas. It underpins self-assembly, phase behavior, and binding phenomena in chemistry and materials science.

See also Coulomb's law, Newtonian gravity, van der Waals forces, Lennard-Jones potential.