|Steel on Steel||0.74||0.57|
|Aluminum on Steel||0.61||0.47|
|Copper on Steel||0.53||0.36|
|Rubber on Concrete||1.0||0.8|
|Wood on Wood||0.25 - 0.5||0.2|
|Glass on Glass||0.94||0.4|
|Waxed wood on Wet snow||0.14||0.1|
|Waxed wood on Dry snow||-||0.04|
|Metal on Metal (lubricated)||0.15||0.06|
|Ice on Ice||0.1||0.03|
|Teflon on Teflon||0.04||0.04|
|Synovial joints in humans||0.01||0.003|
Answered by: Ertan Salik, M.A. Physics, USC
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