If two objects are rubbed together and there is no force pushing them together, then friction is not created. Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. It arises due to the microscopic irregularities on the surfaces that interlock, causing resistance. When objects are rubbed together, these irregularities interact, leading to friction.
The force that pushes the objects together is the normal force, which is the force exerted by a surface to support the weight of an object resting on it. If there is no normal force or if it is insufficient, there is less contact between the surfaces, reducing the potential for interlocking irregularities. As a result, the frictional force diminishes.
In practical terms, this lack of normal force often occurs in scenarios involving objects in free fall or lifted off a surface. In a vacuum or microgravity environment, where there is no supporting surface to exert a normal force, friction is essentially nonexistent.
In summary, the presence of a normal force is crucial for the generation of friction when objects are rubbed together. Without this force, the surfaces experience minimal contact, reducing the likelihood of interlocking irregularities and, consequently, friction.