2. Angular velocity We define the average angular velocity as (8-2) △t The instantaneous angular velocity a is △φd △→0△talt (8-3) Is aa vector quantity? The dimensions of a inverse time(t-l); its units may be radians per second rady s or revolutions per second ( rev/s)We define the average angular velocity as (8-2) The instantaneous angular velocity is (8-3) Is a vector quantity? t av   =   dt d t t    =   =  →0 lim   2. Angular velocity The dimensions of inverse time ( ); its units may be radians per second ( ) or revolutions per second ( ). −1  T rad /s rev /s