[Corvettaholic]

What two surfaces rub together, there of course is friction. This results in heat, sparks, abrasions, whatever. How do you determine energy output of scraping any particular materials together? Wondering if there's a formula, or some good reading, you guys might have a link to. Main thing is heat output of iron on iron, and iron on aluminum.

[Mitch]

This is a rough guide, I'm not sure how much you have learned. What is your educational background?
The coefficient of static friction is what your looking for. It's measured roughly(I have to say roughly or physicist will yell at me) by elevating the two materials at an angle and seeing at what angle the material begins to slide pass each other.

You might be more interested in only the coefficient of kinetic friction(which is the friction between "rubbing") instead of the coefficient of static froction. But the oefficient of static froction will give you the maximum value since...

 coefficient of static froction > coefficient of kinetic friction

You can find these numbers out by either doing the experiement or look it up in the handbook of chemistry and physics.

[Corvettaholic]

My educational background is high school chem and physics, and whatever else I've learned on my own. I always like reading stuff over the net, cause thats the only time I have to look into the neat world of science. at work, that is. I remember vaguely about kinetic friction from my physics class of 5 years ago, but static friction is kind of new to me. Sounds like it has something to do with inertia?

[ssssss]

My educational background is high school chem and physics, and whatever else I've learned on my own. I always like reading stuff over the net, cause thats the only time I have to look into the neat world of science. at work, that is. I remember vaguely about kinetic friction from my physics class of 5 years ago, but static friction is kind of new to me. Sounds like it has something to do with inertia?

Friction is little because of irregularities,abbrasions etc.The main cause of friction is the attraction between the matter of the objects.This is gravitational force which becomes considerable when objects comes too close.Friction does not depend on area of contact of the objects.And there are experiments to prove this law.

[eugenedakin]

Hello Corvettaholic,

I am interested in the circumstance in which sssssss mentiones that friction does not depend on the area of contacts of the objects.  To my understanding, almost all areas of friction do depend on the areas of contact.  My example would be inside an internal combustion engine... lets pick the connecting rods for instance.  Dynamic friction would be less on a moving connecting rod with a larger surface area (this is the reason why dragster engine have larger diameter bearings and greater surface areas, so that the friction can be minimized in these high horsepower engines).

Dynamic friction is the friction produced when two bodies are already in motion, and continue to be in motion.

Static friction is the initial force (or energy) that must be overcome to start a body in motion (typically, initially higher than dynamic friction).  

A small surface area will increase the friction (and disfiguration) of metal.  This can be seen when taking a screwdriver and etching a piece of metal, its fairly easy to do.  However, take a flat 10 square inch piece of metal and try and disfigure the original piece of metal.  It can be done, but it takes signifacently more pressure, and energy to disfigure the metal.  This is because the large contact area of the objects spread the force over a wide area.
I hope this clarifies your question.

Sincerely,

Eugene