2)平均速率U O1dN1+02dM2+…+v0v+…+OndN odn L uNf (o)da 8kT Al 0f(0)d7 gEnn kT RT 7≈1.60 1.60N N N i Ni n Nn d d d d 1 1 2 2 v v v v v + + + + + =   2）平均速率 v N Nf N N N    = = 0 0 vd v (v)dv v m kT f π 8 ( )d 0 = =   v v v v M R T m kT v 1.6 0 =1.6 0 v f (v) o