force

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