Friction is a complex phenomenon that is of paramount importance in everyday life. We present an easy-to-build and inexpensive experiment illustrating Coulomb's law of kinetic friction. The so-called friction, or Timoshenko, oscillator consists of a plate set into periodic motion through the competition between gravity and friction on its rotating supports. The period of such an oscillator gives a measurement of the coefficient of kinetic friction μk between the plate and the supports. Our prototype is mainly composed of a motor, LEGO blocks, and a low-cost microcontroller, but despite its simplicity, the results obtained are in good agreement with values of μk found in the literature (enhanced online).
A study of kinetic friction: The Timoshenko oscillator
Robin Henaff, Gabriel Le Doudic, Bertrand Pilette, Catherine Even, Jean-Marie Fischbach, Frédéric Bouquet, Julien Bobroff, Miguel Monteverde, Claire A. Marrache-Kikuchi; A study of kinetic friction: The Timoshenko oscillator. Am. J. Phys. 1 March 2018; 86 (3): 174–179. https://doi.org/10.1119/1.5008862
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