1452 
For a partiele M, in statistical equilibrium with molecules m, 
this factor amounts to: 
6 , M ne M VA Mm P ai or NU Vee 
& SS SS So = = => OG (Si A = 
Rad *“M+m *m(M4m) M+m ool a M a M m 
M 
If is large (and in the case under consideration this is so) we 
m 
m 
may develop @ to the first power of ae which causes the above 
a 
expression to become simplified to 
0 De 1 
Mii Een 
ien > M 
Let us now call the velocity of the particle at a given moment 
S, (u,v, wW,). When during a time rt, it has travelled with this velocity, 
it collides with a molecule with velocity s', (w’, v 
Ul 
, w',), and gets 
therefore itself a velocity s,. This again consists of 2 parts: 
1. The velocity of the centre of gravity, on an average = Ó js, 
2. A component that can have all possible directions, is O on 
m 
an average, and whose value = Me V,, when V’, represents the 
M+ m 
relative velocity of the particle and the molecule before the collision 
(AB of fig. 1). 
For u, we can now on an average draw up the relation : 
m 
M -L m 
Oud VERCOSLA Te (2) 
À 
the collision. 
In r, a distance along the z-axis is passed over: 
, is the angle between the z-axis and the relative movement after 
in T, 
§, = U, Tt 
2 anne 
v 
In a time (= XT this distance amounts to: 
1 
NES 
1 1 
If we now suppose that always a time r passes between two colli- 
sions, we can bring this quantity outside the © sign, and write: 
v 
ANS. 
1 
