keskivoima
Keskivoima, or central force, is a force between a particle and a central point that acts along the line joining the particle and the center and whose magnitude depends only on the distance r from the center. Central forces are a common idealization in classical mechanics and celestial mechanics because they preserve angular momentum and constrain motion to a plane.
Mathematically, the force is F(r) = F(r) r_hat, where F depends only on r. In plane polar coordinates,
Examples include the gravitational force F = -G M m / r^2 and the electrostatic force F = k
Applications of keskivoima appear in celestial mechanics, atomic and molecular physics, and any system with dominant