Centripetale

Centripetale, in English centripetal, refers to a property of motion along a circular or curved path in which the velocity changes direction toward the center of the circle. The inward acceleration toward the center is called centripetal acceleration. It is not a distinct force; rather, it is the inward component of the net real force acting on the object.

For an object moving with speed v along a circle of radius r, the magnitude of the centripetal acceleration is a_c = v^2 / r = ω^2 r, where ω is the angular speed. The inward force that produces this acceleration satisfies F_in = m a_c, with direction toward the center. If multiple forces act, their radial components toward the center sum to provide the centripetal force.

Examples illustrate the concept: gravity provides the centripetal force for planets orbiting the Sun; the tension in a tether provides the inward force for a mass on a string swung in a circle; friction and normal forces can provide centripetal forces for a car turning along a horizontal curve; a conical pendulum involves a balance that yields inward centripetal acceleration.

In a rotating frame of reference, an outward centrifugal force appears as a fictitious force, whereas in an inertial frame the centripetal force is the real inward force directing the motion. In non-uniform circular motion, there can also be tangential acceleration, while the centripetal component remains the inward part of the acceleration toward the center.