Contact Area and its Relation to Friction?

[lukevanoort]

Originally Posted by Woody1458

Also as an answer to the question mu the mathmatical ratio of the force of friction/normal force is unique not only for every material but for every object. Thus, the contact area is calculated in when stating mu. I couldn't give you a mu of rubber on asphalt, but i could give you a mu of a specific tire with a specific contact area and texture.

Sort of. In classical friction you ignore the effect of surface area and the mu doesn't take it into account, which provides a very good approximation with hard materials. On the other hand, with interlocking materials (which I am still not convinced applies to FIRST carpet), there is something of an effect from surface area, but it is probably (I have never tried) a bit hard to predict well enough to warrant including in calculations. While the best results for traction tests would be between the same two objects (manufacturing irregularities would get taken into account) and testing them, similar objects can work pretty well. For example, if I wanted a very accurate number for how much traction a robot has, I would take it to a competition field with a force gauge. Unfortunately, that is unrealistic, so one can just test with a sample of the material on similar (ideally the same) carpet, and still get pretty decent numbers.