Rotation itself does not directly cause friction. Friction is the force that opposes the relative motion or tendency of motion between two surfaces in contact. It arises due to the interactions between the atoms or molecules on the surfaces of the objects.
When an object rotates, friction can come into play in a couple of ways:
Sliding Friction: If one surface is rotating against another surface, and there is relative motion or a tendency of motion between them, sliding friction can occur. This happens when the surfaces are in contact and moving against each other tangentially, creating resistance to the motion. Sliding friction is responsible for phenomena like the slowing down of rotating objects or the stopping of rotating parts.
Rolling Friction: When a round object, such as a wheel or a ball, rolls on a surface, rolling friction comes into play. Rolling friction is generally lower than sliding friction because the object rolls rather than sliding or dragging across the surface. However, rolling friction still exists due to the deformation of the object and the interaction between the two surfaces in contact. Rolling friction can be influenced by factors such as the roughness of the surfaces, the weight of the object, and the materials involved.
In both cases, the friction arises from the intermolecular forces between the surface atoms or molecules. These forces can lead to the generation of heat and the dissipation of energy, resulting in the slowing down or resistance to the rotational motion.