It is very common to see people referring to centrifugal force when talking about circular motion. Imagine, for example, a sphere attached to a string and in uniform circular motion, under the centripetal force (F c ) acting on the string. Many people have the habit of assuming the existence of another force, called centrifugal force (F cf), which acts on the sphere. According to these people, this force would be balancing the other force that acts on the string. This assumption is wrong, because the centrifugal force does not exist, because if that happened the resultant force on the sphere would be zero and therefore it could not be describing uniform circular motion. If so, the motion of the sphere would be straight and uniform according to Newton’s first law, the law of inertia.
