A block sliding down an inclined plane normally accelerates. However, if the friction force increases with speed, then the block can slide at a constant terminal speed in a manner similar to the fall of an object through a fluid. Measurements of the increase in the coefficient of friction for tennis ball cloth sliding on a smooth surface are described over speeds varying by a factor of 9000. For the low speed measurements, the ball cloth was attached to the bottom of a weighted box and pulled along a horizontal surface by a constant horizontal force. Results. at higher speeds were obtained by bouncing a tennis ball off the surface. (c) 2005 American Association of Physics Teachers.
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