kinetic friciton

Now I get to do something with that force scale I built. I had a request some time ago to talk about friction. Friction is surprisingly complicated. When two surfaces rub against each other, why is there a friction force? The basic answer is that the stuff the two surfaces are made of (atoms) are interacting with each other. If you like, you could think of the bumps on one surface hitting the bumps on the other surface. I know I said it was complicated and that doesn't seem to complicated - does it? The complication comes when you try to model this interaction by looking at either all…