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Friction is the force resisting the relative motion of solid surfaces, fluid layers, ... Coulomb investigated the influence of four main factors on friction: ...
This theory is exact for the situation of an infinite friction coefficient in which case the slip area vanishes, and is approximative for non-vanishing creepages. It does assume Coulomb's friction law, which more or less requires (scrupulously) clean surfaces. This theory is for massive bodies such as the railway wheel-rail contact.
In addition, only the so-called slip resistance involves friction, therefore the name "rolling friction" is to an extent a misnomer. Analogous with sliding friction, rolling resistance is often expressed as a coefficient times the normal force. This coefficient of rolling resistance is generally much smaller than the coefficient of sliding ...
Jean Le Rond d'Alembert, Nouvelles expériences sur la résistance des fluides, 1777. In fluid dynamics, friction loss (or frictional loss) is the head loss that occurs in a containment such as a pipe or duct due to the effect of the fluid's viscosity near the surface of the containment.
Which friction factor is plotted in a Moody diagram may be determined by inspection if the publisher did not include the formula described above: Observe the value of the friction factor for laminar flow at a Reynolds number of 1000. If the value of the friction factor is 0.064, then the Darcy friction factor is plotted in the Moody diagram.
Stokes' law is the basis of the falling-sphere viscometer, in which the fluid is stationary in a vertical glass tube.A sphere of known size and density is allowed to descend through the liquid.
The shear resistance of soil is a result of friction and interlocking of particles, and possibly cementation or bonding of particle contacts. Due to interlocking, particulate material may expand or contract in volume as it is subject to shear strains. If soil expands its volume, the density of particles will decrease and the strength will ...
The friction drag force, which is a tangential force on the aircraft surface, depends substantially on boundary layer configuration and viscosity. The net friction drag, , is calculated as the downstream projection of the viscous forces evaluated over the body's surface. The sum of friction drag and pressure (form) drag is called viscous drag.