A force whose line of action is always directed toward a fixed point. The central force may attract or repel. The point toward or from which the force acts is called the center of force. If the central force attracts a material particle, the path of the particle is a curve concave toward the center of force; if the central force repels the particle, its orbit is convex to the center of force. Undisturbed orbital motion under the influence of a central force satisfies Kepler's law of areas.
a force that is applied to a material body and whose line of action, regardless of the position of the body, passes through some specific point called the center of force. Examples of central forces include gravitational forces, which are directed toward the center of the sun or of a planet, and the electrostatic forces of attraction and repulsion. Under the influence of a central force, the center of mass of an unrestrained body moves along a plane curve and the line segment that connects the center of mass and the center of force sweeps out equal areas in equal intervals of time (seeLAW OF AREAS). The theory of motion under the influence of a central force has important applications in celestial mechanics, for example, in the calculation of the motion of spacecraft and artificial satellites.