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Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. [2][3] Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of the processes involved is called tribology, and has a history of more than 2000 years.
Contents. Moody chart. In engineering, the Moody chart or Moody diagram (also Stanton diagram) is a graph in non-dimensional form that relates the Darcy–Weisbach friction factor fD, Reynolds number Re, and surface roughness for fully developed flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe.
hide. In fluid dynamics, the Darcy–Weisbach equation is an empirical equation that relates the head loss, or pressure loss, due to friction along a given length of pipe to the average velocity of the fluid flow for an incompressible fluid. The equation is named after Henry Darcy and Julius Weisbach.
Floor slip resistance testing is the science of measuring the coefficient of friction (or resistance to slip accidents) of flooring surfaces, either in a laboratory (before or after installation) or on floors in situ. Slip resistance testing (or floor friction testing) is usually desired by the building's owner or manager when there has been a ...
Adhesion railway. Driving wheel of steam locomotive. An adhesion railway relies on adhesion traction to move the train, and is the most widespread and common type of railway in the world. Adhesion traction is the friction between the drive wheels and the steel rail. [ 1 ] Since the vast majority of railways are adhesion railways, the term ...
is the rolling resistance coefficient or coefficient of rolling friction with dimension of length, and N {\displaystyle N} is the normal force (equal to W , not R , as shown in figure 1). The above equation, where resistance is inversely proportional to radius r {\displaystyle r} seems to be based on the discredited "Coulomb's law" (Neither ...
The coefficient of restitution (COR, also denoted by e), is the ratio of the relative velocity of separation after collision to the relative velocity of approach before collision. It can also be defined as the square root of the ratio of the final kinetic energy to the initial kinetic energy. It normally ranges from 0 to 1 where 1 would be a ...
Schematic of a liquid drop showing the quantities in the Young equation. The contact angle (symbol θC) is the angle between a liquid surface and a solid surface where they meet. More specifically, it is the angle between the surface tangent on the liquid– vapor interface and the tangent on the solid–liquid interface at their intersection.