When does Rolling Friction come into play?

Question

According to Wikipedia, "Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface."

But at the same time, it is the static friction that is responsible for the forward movement of the wheels of a vehicle, according to many sources. But by the above definition, should it not be the rolling friction that comes into play?

I had also found rolling friction to be defined as follows: "Rolling resistance tends to be a catch all term for the energy dissipated in the many moving parts as a vehicle moves."

(For more, please visit Rolling resistance and static friction )

1) So, which definition is the right one?

2) Also, which friction is applicable for the motion of the wheels of a vehicle?

3) The motion of the wheels of a vehicle is considered "rolling without slipping". I know this sounds stupid, but does the condition "rolling and slipping" exist?

Answer 1

Static friction is what keeps the object rolling (where molecules of the object and the surface essentially act like cogs in a wheel).

Rolling friction refers to the processes of rolling that cause kinetic energy to be turned into heat (which by definition can't be static friction). For example, a rolling basketball becomes slightly deformed (the part touching the ground is smushed in/not perfectly spherical) as it rolls - more so the less it's inflated. That deformation absorbs kinetic energy as heat.

If you have an axle in a car, then you can lump the friction of the axle into rolling friction since it's not a scientifically rigorous definition.

For rolling and slipping, imagine tires on ice. Slipping leads to kinetic (and not just static) friction.