Friction force is a force which opposes motion and acts in the opposite direction to the motion.Friction is a force that is created whenever two surfaces move or try to move across each other..
- Dry friction resists relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into static friction ("stiction") between non-moving surfaces, and kinetic friction between moving surfaces.
- Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other.
- Lubricated friction is a case of fluid friction where a fluid separates two solid surfaces.
- Skin friction is a component of drag , the force resisting the motion of a fluid across the surface of a body.
- Internal friction is the force resisting motion between the elements making up a solid material while it undergoes deformation.