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The friction coefficient is an empirical (experimentally measured) structural property that depends only on various aspects of the contacting materials, such as surface roughness. The coefficient of friction is not a function of mass or volume. For instance, a large aluminum block has the same coefficient of friction as a small aluminum block.
Micrometre or micron (retired in 1967 as a standalone symbol, replaced by "μm" using the standard SI meaning) the coefficient of friction in physics; the service rate in queueing theory; the dynamic viscosity in physics; magnetic permeability in electromagnetics; a muon; reduced mass; the ion mobility in plasma physics
the coefficient of friction (also used in aviation as braking coefficient (see Braking action)) reduced mass in the two-body problem; Standard gravitational parameter in celestial mechanics; linear density, or mass per unit length, in strings and other one-dimensional objects; permeability in electromagnetism
coefficient of friction: unitless (dynamic) viscosity (also ) pascal second (Pa⋅s) permeability (electromagnetism) henry per meter (H/m) reduced mass: kilogram (kg) Standard gravitational parameter: cubic meter per second squared mu nought Vacuum permeability or the magnetic constant
μ (some authors use the symbol η) is the dynamic viscosity (Pascal-seconds, kg m −1 s −1); R is the radius of the spherical object (meters); is the flow velocity relative to the object (meters per second). Note the minus sign in the equation, the drag force points in the opposite direction to the relative velocity: drag opposes the motion.
In fluid dynamics, the Darcy friction factor formulae are equations that allow the calculation of the Darcy friction factor, a dimensionless quantity used in the Darcy–Weisbach equation, for the description of friction losses in pipe flow as well as open-channel flow.
Standard symbol Definition Field of application Coefficient of kinetic friction: mechanics (friction of solid bodies in translational motion) Coefficient of static friction: mechanics (friction of solid bodies at rest) Dieterich-Ruina-Rice number
where is the density of the fluid, is the average velocity in the pipe, is the friction factor from the Moody chart, is the length of the pipe and is the pipe diameter. The chart plots Darcy–Weisbach friction factor f D {\displaystyle f_{D}} against Reynolds number Re for a variety of relative roughnesses, the ratio of the mean height of ...