ROLLING MOTION AND CRUMPLED SURFACES

We discuss some aspects of a paper which appeared recently in this jou rnal [F. F. Lima, V. M. Oliveira, and M.A.F. Gomes, Am. J. Phys. 61, 4 21-422, 1993] in which the fractional dimension of rolling crumpled su rfaces is measured experimentally. We show that this experiment may no t actually be measuring fractal dimension kinematically at all. In add ition, we report a variation of their experiment using. nonfractal gro oved cylinders. The results indicate that large irregularities on the surface of ''rolling'' objects may lead to errors in the dynamic measu rement of the dimension of crumpled surfaces. (C) 1995 American Associ ation of Physics Teachers.