Centrifugal force

Centrifugal force is the experience of the inertia of an object moving in circular motion, causing it to move away from the center. It is not a force.

Velocity is a vector quantity; that is, it has magnitude (speed) and direction. If a body has constant velocity, it is travelling at a constant speed in a constant direction ie in a straight line. If a body is travelling at a constant speed in a circle, its direction and thus its velocity is constantly changing.

We know from Newton's first law of motion that a body will maintain a constant velocity unless a net force (the sum of all the forces acting) acts upon it. Thus when a body travels in a circle a net force must be applied to stop it from travelling in a straight line. This force is the centripetal force, the only action force necessary for a circular motion. It is accompanied by a reaction force - on the object providing the centripetal force - by Newton's third law of motion.

What is sometimes interpreted as a "centrifugal force" is its inertia, which would cause it to move in a straight line, tangent to the circle, if not for the centripetal force.

Physics teachers are keen to teach that the real force is centripetal force and that centifugal force is the reactionary force which balances it. Conversion of angular momentum into linear momentum is used in a number of ways, the most obvious is perhaps a sling.

See also: Coriolis force, centrifugation, trebuchet