Centrifugal force

The centrifugal force is an inertial force experienced in a rotating reference frame acting away from the center of the rotation. It is equal in magnitude but opposite to the centripetal force required to constrain the body to move in a circular motion.

Velocity is a vector quantity; that is, it has magnitude (speed) and direction. If a body is travelling at a certain speed and in a certain direction undisturbed it has constant velocity. Thus if a body is travelling at a constant speed in a circle, its velocity is constantly changing.

We know from Newton's first law that a body will retain its velocity unless another force acts upon it. Thus when a body travels in a circle a force must be applied to stop it from travelling in a straight line. This force is the centripetal force, the only force necessary for a circular motion. What is interpreted sometimes as a centrifugal force is the tendency of the object to follow in a straight line, which would bring it outside of its circular trajectory.

See also: Coriolis force