Some Considerations on Centrifugal Force in Education

Abstract

The topic of circular motion has a long history of confusion and the controversy regarding how to define centrifugal force and how to teach it had erupted for twenty years in The American Journal of Physics. In 1935, C. F. Hagenow pointed out that the definitions of centrifugal force were either incorrect, misleading or unnecessarily vagu and he proposed that it is probably better to refrain from the use of the idea of inertial force altogether in elementary treatments. After that, the meaning of the term centrifugal force was discussed in the journal by many physics teachers. The vogueness of textbooks handling centrifugal force is pointed out by many people. J. A. Struthers analized the textbooks primarily for elementary and high school use and identified the several meanings of centrifugal force. The use of the term centrifugal force with three different usages was observed and the first usage occurred three times as frequently in physics books as in other types. The authors surveyed the textbooks and found out that most of the elementary textbooks in America define the centrifugal force as the reaction of centripetal force. Also in Japan, the textbooks of middle school under the old system defined generally the centrifugal force as the reaction of centripetal force, but now in Physics B of the senior high school, the centrifugal force is defined as the radial force exerted by a radial force outward on a rotating mass postulated to make inertial laws valid in an accelerated frame of reference. Many physics teachers proposed the recommendations bringing order into this chaotic situation in regard to circuler motion but at the first step it is essential that we put an accurate and usefull definition of centrifugal force. The authors have often been told that the mistaken ideas taught in elementary courses do not matter as they will be corrected in later teaching. This hope is no doubt generally derived from a misunderstanding of the nature of the nature of the errors. There is all the difference in the world between a valid approximation and a mistak.