Radian per second Radian per second The radian per second (symbol: rad·s or rad/s) is the SI unit of rotational speed (angular velocity), commonly denoted by the Greek letter "ω" (omega). The radian per second is also the unit of angular frequency. The radian per second is defined as the change in the orientation of an object, in radians, every second. Since the radian is a dimensionless unit, the radian per second is dimensionally equivalent to the hertz—both are defined as s. This may lead to confusion between the quantities angular frequency "ω" and frequency "ν". A use of the "unit radian per
Collision frequency Collision frequency Collision frequency is defined in chemical kinetics and collision theory, in the background of "theoretical kinetics". If a system contains "n" type-a molecules per unit volume and "n" type-b molecules in that same unit volume, then the number of a-b collisions per unit time in that volume will be proportional to the product "nn". or, in terms of molar volumes ("[x]=n /N" where N is the Avogadro constant) By kinetic theory it can be shown that: where The collision frequency ("Z") is usually expressed in units of "moles of collisions" per unit time per unit volume: or equivalently: