Center of Mass Correction to an Error-Prone Undergraduate Centripetal Force Experiment

Document Type

Article

Publication Date

2-1-2003

Department

Physics and Astronomy

Abstract

In this undergraduate laboratory experiment we measure the centripetal force acting on a bob in uniform circular motion. As the experiment was originally designed, it consistently yielded large errors due to a subtle twist of the bob as the mass was increased incrementally. This error is due to the fact that the center of mass changes relative position as the mass is incremented; therefore, the spring that provides the centripetal force for the apparatus causes an unintended torque on the bob. A solution to the problem consists of positioning the incremental masses so that the center of mass does not change position. This simple correction provides a useful lesson on redesigning an undergraduate laboratory experiment to obtain better agreement with theory. (C) 2003 American Association of Physics Teachers.

Publication Title

American Journal of Physics

Volume

71

Issue

2

First Page

185

Last Page

188

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