friction between two flat surfaces can be divided into categories. what are the two most common kinds of friction?
A. Air resistance
Its not A because or resistance is the force of an object passing through air.
Its not B because kenetic is the energy in motion.
Its not C because fluid force is the force of water on an object.
Its D because static friction is when one object is on top of another or resting. Which can be two seperate surfaces. And they can be divided into two categories. Also D if you are asking for 1 answer.
But if you are asking for the two most common types of friction, its static and kenetic. Because friction between two flat surfaces is either static or kenetic friction.
Hope this helps ;P