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Figure 1 Hard wheel rolling on and deforming a soft surface, resulting in the reaction force R from the surface having a component that opposes the motion. (W is some vertical load on the axle, F is some towing force applied to the axle, r is the wheel radius, and both friction with the ground and friction at the axle are assumed to be negligible and so are not shown.
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. If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube.
[1] [8], for a wide channel this is approximately equal to the water depth; is the hydraulic gradient, which for uniform normal depth of flow is the slope of the channel bottom [unitless; length/length]; is Chézy's coefficient [length 1/2 /time]. Values of this coefficient must be determined experimentally.
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.
The capstan equation[ 1 ] or belt friction equation, also known as Euler–Eytelwein formula[ 2 ] (after Leonhard Euler and Johann Albert Eytelwein), [ 3 ] relates the hold-force to the load-force if a flexible line is wound around a cylinder (a bollard, a winch or a capstan). [ 4 ][ 1 ] It also applies for fractions of one turn as occur with ...
Dimension. L T−3. Jerk (also known as jolt) is the rate of change of an object's acceleration over time. It is a vector quantity (having both magnitude and direction). Jerk is most commonly denoted by the symbol j and expressed in m/s 3 (SI units) or standard gravities per second (g0 /s).
Shear velocity. Shear velocity, also called friction velocity, is a form by which a shear stress may be re-written in units of velocity. It is useful as a method in fluid mechanics to compare true velocities, such as the velocity of a flow in a stream, to a velocity that relates shear between layers of flow. Shear velocity is used to describe ...
The former is concerned with static friction (also known as "stiction" [3]) or "limiting friction", whilst the latter is dynamic friction, also called "sliding friction". For steel on steel, the coefficient of friction can be as high as 0.78, under laboratory conditions, but typically on railways it is between 0.35 and 0.5, [ 4 ] whilst under ...