Resumen

MANZUR, A. Cuando la fuerza de fricción estática se convierte en fuerza de fricción cinética y viceversa. Rev. mex. fís. E [online]. 2008, vol.54, n.1, pp.51-54. ISSN 1870-3542.

The demonstration experiment here presented illustrates the behavior of static and kinetic friction forces on the sliding motion of a rigid body. It is also illustrated that these forces are not constant, in general. The objectives are satisfactorily gotten using a bar or an object which has a straight part, as a broom. The bar is placed horizontally on the index fingers; the fingers are sliced until they meet beneath the center of mass or they separate until one of them reach one end of the bar. When the fingers are brought together the bar slides alternately over only one finger; however, when they are separated, the sliding motion of the bar is produced without the alternation

Palabras llave : Demonstration experiments; teaching methods; center of mass; friction force.

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