Friction conditions on contact point of disc

[mavk]

Hello,

I have some doubts regarding the friction force on a certain situation. Imagine a disc over a fixed flat surface. Like this:

The disc has two motions, rotational and translational but these are independent of each other. I mean the translational motion does not come from the rotation of the disc, imagine an external force that moves the disc.

Now, with this in mind let's say that the disc is moving from left to right always keeping contact with the surface. At the same time the disc is rotating with an angular velocity clockwise. Because of the different movements, at the contact point, there is slip.

Now to the question itself. What kind of friction do I have at the contact point? Do I have rolling or sliding friction at the contact point? and what direction does the friction force have since the disc is moving to the right but at the contact point the direction of rotation is to the left?

Thank you.

 

[LightHero]

The friction force at the contact point would be a combination of rolling and sliding friction. The magnitude and direction of the friction force will depend on the relative velocity between the two surfaces. If the disc is moving faster than the rotation, then the friction force will point in the same direction as the translational motion. If the rotation is faster than the disc's motion, then the friction will point in the opposite direction.