Velocity

high-resolution terminology - matching measurements at high-resolution

Velocity

Description

Velocity, v [m/s], is the speed in a defined spatial direction, and as such velocity is a vector. Velocity is the advancement of distance per unit time,

v ≡ dz ∙ dt-1 [m/s]

Abbreviation: v

Reference: Gnaiger 2018 MiPschool Tromso A2

MitoPedia concepts: Ergodynamics 

Communicated by Gnaiger E 2018-10-20

Velocity in diffusion

When a force acts on a particle X in direction z, it causes an acceleration, thus increasing the velocity of the particle up to a stationary state, when the effect of the force is counteracted by the frictional resistance. At this stationary state, the potential for performing work (erg; exergy) is not any longer conserved in kinetic exergy (acceleration), but is dissipated such that the exergy driving the process is consumed only to maintain the particle at constant velocity. Then the motive particle has an average velocity v in the z direction, relative to any reference velocity, irrespective of its speed following the pattern of Brownian motion. Since v is a vector with information on magnitude and spatial direction, it is written in bold face,

v ≡ dz ∙ dt-1 [m/s]

The velocity at stationary state is proportional to the motive force, with the mobility, u'NX, as the proportionality constant,

v = -uNX ∙ dmFNX [m/s]

For a number of uncharged motive particles or molecules, NX, diffusing at velocity v, the corresponding flow of diffusion, IdNX, across a plane perpendicular to the gradient in direction z is,

IdNX = NX ∙ v [x∙m∙s-1]