Which type of friction is always greater than rolling friction?

Kinetic friction is the type of friction that occurs between two surfaces in relative motion. When an object is sliding over a surface, the friction resisting that motion is termed kinetic friction. This type of friction is generally always greater than rolling friction.

Rolling friction is the resistance encountered when an object rolls over a surface, typically being much less than both static and kinetic friction. The reason rolling friction is lower is due to the nature of how the surfaces contact each other during the rolling process, which minimizes the area of contact compared to sliding (as in kinetic friction).

Understanding these distinctions is important in power engineering, as it affects the design and efficiency of machines and systems where movement is involved. Knowing that kinetic friction is typically greater than rolling friction helps engineers predict and mitigate possible energy losses due to friction in mechanical systems.