An interaction that changes the momentum of a body — the cause of acceleration.
four fundamental forces:
- gravity: attraction between masses, curvature of spacetime
- electromagnetism: interaction between charges, carrier of light and radiation
- strong nuclear: binds quarks into protons/neutrons, holds atomic nuclei together
- weak nuclear: mediates radioactive decay and neutrino interactions
Newton's second law: force equals mass times acceleration (F = ma)
in quantum mechanics, forces arise from exchange of gauge bosons in field theory
all macroscopic contact forces reduce to electromagnetism at the atomic scale
conserved quantities (energy, momentum) constrain the effect of forces — see mechanics