Quote:
Originally Posted by JamesTerm
is there some cutoff point where the value changes from one state to another or is it a blend.
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Mu versus relative velocity is an asymptotic curve approaching zero as velocity increases, but there's a small bump up just after you start to slip (very much depends on the surface and wheel material, so not always).
In general, static friction is higher than kinetic friction. Usually.
As for experimental error: Yes, by having the gravity vector point through something other than the bottom(ish) of the robot, you're changing things and that is usually significant.
A better method if you need actual numbers (instead of comparative effects) would be a calibrated pulling device that drags the robot across the test plate.