friktionstal
Friktionstal, or coefficient of friction, is a dimensionless quantity that characterizes the resistance to sliding between two contacting surfaces. It is usually denoted by the Greek letter mu (μ) and is defined as the ratio between the frictional force F and the normal force N acting perpendicular to the contact surface. Two main forms are distinguished: the static (or impending) friction coefficient μs, which limits the frictional force when the surfaces are at rest, and the kinetic (or dynamic) friction coefficient μk, which describes the friction when the surfaces are sliding past each other. In sliding motion, the frictional force is typically F ≈ μk N, while when at rest the friction can vary up to F ≤ μs N.
Historically, Amontons’ laws described friction as proportional to the normal force and largely independent of contact
Friktionstal is widely used in engineering and physics to predict and analyze forces, energy loss, wear, and