( 49f) ) 



N<»l llic l(»!;il i'<'lAti\(' \('l()cil\ .V,. cli.iiiLio its siüii iji a collisidii ol 

 lliis kind. Imt (»iilv the (•(Uii|)()ii('iil ii(ii-iiial lo the taii^ciil plane in 

 tiic |)oinl in which ihc nioN'cnh's lonch (inc aiiolhcr. The impnlsc 

 is llioi-cforc /Il .<,. cos <f . 



The lolal ini|>nls<' of iIk; coMisidn,- of ihc kind nndcr cnnsidcralion 

 will lh('i'ct'(»i-(' 1)(' ('(|nal lo: 



/■'('/. '•. '/■) /■' ("j. '■,. "■,) '/" '/'■ '/"• '/"j '/'■, <lii\ •-->' /•" •-•'// '/ '■'»>■•■' (f i/(f </if'. 



The eili'htfohl inlcural ol' ihis «wprosion vicMs ihc lolal |»r('s>ni-e 

 exercised OJi ihc sni-lace of ihc di>lanc(' spheres. \\'c haxc: 



,()■'- 



(f ros- (f (l(f (l\\i =: .T r 



if we iiilejii-ale aeconlinii' lo if' helwccn the iinnls O and 2 rr and 



1 

 accoi-diiiü- lo <f hotwccn ihc limits O and .t. The linnts lor 7 are 



not O and rr. tor the paris ot' iIh' distance sphere of niolecnle I lor 



1 

 which </ ^ -T. cainiot conie inio collision lor the izixcn relalixc 



\'<'l(»cilv .<,. A\'e may write .v'-j-x/-, lor s,- for ihe teims s s^ cus {s,s^) 

 \ ield /er(» on a\'era.L!('. Doinu' this wc may inte'jrnle the lerm with 

 .v' according' l<> '/'/,. '//", '\\\<\ 'li'\: so wc ud : 



I ^'' (",• '•,• "•,) <f", <l>\ '/"•, ~ " 



The lerm with .<,'- on the other hand may he inteur.iled accoi-ding- 

 lo (hl , (Ir and ilic: so we L!('t : 



j 



/• {i(. r . ir) il II il r il ir — 



'J'his xiehls lor ihe total pressnre 011 the snrface of the di>laiice 

 spheies : 



2 



- .T /■- i( 



j /// s" /•' {,(. r. ir) ,hi ilr ,hr -\- j /// .v,""' /' (ii ^. /•,. ""J ,lii^ ,1 r ^ ,lir^ 



lloih inle.Lirals in this expression are eipial to mus'-. ///.>•- repi-esenl- 

 hiji- twice ihe mean kinelic enei-,Liy of a molecnle. \\ e may there- 

 loiv wi-ile lhi> e\|>re>sion as follows: 



4 ^ — 



rr )•' ir ms- . 



l)i\idinLi- this ([nantil\ l>y the total surface of the distance spheres 

 4.T /•■>/. we üet for ihe \aliie of the a\era,L!.e pressmv: 



1 - 



— n ms' 

 3 



