Mu and Friction
Today in physics class, we learned about "mu" (the Coefficient of Friction) and how to calculate it. We also did a "Mu of the Shoe Lab" and reviewed how to draw FBDs. I could go into some deep technicalities (which I might do just to review from now on), but for now I will leave it alone.
Friction is a force that causes tension between two surfaces; it slows objects down as well usually. Friction seems to be dependent on texture, right? For example, a smooth, linoleum basketball stadium floor would have less friction than an asphalt road due to the texture of both surfaces. The difference with the basketball stadium is that it's a linoleum (smoothed over floor) with probably no dents or crevices or anything. On the other hand, asphalt is bumpy and rocky as hell! There are cracks, potholes, crevices, etc. So keeping that in mind, maybe when something rubs over those surfaces the particles in each type surface may be the reason for friction.
Think about it, when we rub our hands we cause friction and you feel what after a while? Heat! Where does heat come from? Kinetic energy! Kinetic energy is in and is transferred and can go up with motion. You probably need energy to overcome the roughness of a surface as the particles clash and what not. Friction probably causes a very small amount of energy transfer too (hot to cold :3).
I'm probably wrong and all, but this is my theory and I mean friction makes sense to me yet I have no way to reason it so that's a good question.
In general, a rough surface would cause a greater mu because there would be more friction from a rough surface.
Some examples are as follows:
- A sandpaper surface (ow :-()
- Asphalt
- Grass
- Tire surfaces
- Velcro or felt surface
Regardless of the weight of my shoe or whatever, the friction would still be higher in comparison to these surfaces so let's get that out of the way. I believe that the mu would be higher with my converse shoes when dragged across, say, an asphalt surface because asphalt's kind of rougher than carpet and what not. Most people can easily get a scrape from asphalt, in fact (though there's probably more to friction than simply just roughness but still). Also, since mu = Ff/FN and FN is the weight of my shoe, if the friction increases so does the mu because the mu is a ratio. Think of it this way let's say my shoe weighs 2 N and the friction when dragged across a table is 2 N. 2 N/2 N = 1. But let's say when dragged across an asphalt surface the friction is 20 N (such a reasonable amount pptptpf), then 20 N/2 N = 10. If the friction's higher when I drag my shoe across an asphalt surface then I'll get a high mu. And hey, most objects on asphalt need gas power to overcome friction so I'm sure there's a fair amount of friction in an asphalt road or surface (especially the older ones).
Have mu jokes =^w^=!~:
Annnnnd, just because xD.
