Coefficient of Friction
The coefficient of friction is a unit less ratio of the force of friction to the normal force. The real value for the coefficient is often determined experimentally. In ski racing there are several factors that contribute to the coefficient of friction. Some of these factors include but are not limited to, area in contact, snow condition, wax, condition of ski, and speed. Some of these are completely out of the control of the racer. Wax and ski condition is probably the easiest of the above mentioned for the racer to control. He can wax for the right snow conditions to reduce the coefficient. Further a well maintained ski will have a flat base with no impurities in the texture reducing the coefficient.
The coefficient of friction between the ski and snow is greatly reduced from the coefficient of every day life. The usual range for the coefficient of kinetic friction is 0.3 to 1. The Synovial joints in a human have a coefficient of 0.003. Ice on ice has a coefficient of 0.03. The coefficient of friction between a hydrophobic plastic, the same material as a ski base, is 0.03. This value for the coefficient of friction is an order of one magnitude less then that found in normal day life. On average, the coefficient of an automobile tire on dry pavement is 0.8.
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These incredibly low values for the coefficient of friction allow for some amazing speeds. The world record for speed skiing is 151+ mph set by Jeff Hamilton in Les Arc, France (pictured above). This is the world record for the fastest man on skis. In downhill ski racing the maximum speeds are about 65 mph slower then this speed. The reason for this lower speed is competitive downhill ski racing requires turns; therefore, the skis are not run perfectly flat and straight so maximum speed is not attained. Downhill ski racing is a balance between gliding and turning.
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TWO ASPECTS OF DOWNHILL RACING: