Why doesn't a larger surface area produce a lot more friction than a smaller one?

Answer 1

As you know, the frictional force depends only on the coefficient of friction and the normal force, not on the area. That means that a force of 20 Newtons spread over one square meter of a surface will produce as much frictional force as that same 20 Newtons spread over 1/10 of a square meter. In the latter case, the force is much more concentrated, exactly in inverse proportion to the amount of the area.

So, in a sense, the area does count, but the force per unit area is exactly inversely proportional to the size of the area, so they balance out.

Answer 2

It does.

But the friction force depends on the pressure, and a larger area spreads the load and so produces lower pressure. Because pressure is inversely proportional to area, and friction proportional to it the net result is that for a given load the area cancels.

Answer 3

with larger area, the inertia may be more? Am I right?... Just a thought..... I am away from textbooks.
When tire has less air then more area is in contact with road. This causes the engine to work more. So the frictional force may be same but total 'work' required to complete same task is more.
So, what u r looking for is... that ... amount of work increases with area.. You can express this in mathematical terms if you look at equation of 'work'.

Answer 4

This holds true to a point, excuse the pun. There is some limiting factor on just how small an area will work for this assumption. I don't know what that is, but if you concentrate a load to the area of a needle point, things change.