; Þ (29)
(28) (29),
(30)
(30) , u - . ,
.
. . : , s - (/ 2), , (). D , .
r D xS × = F (x +D x)+ F (x), (31)
r - , S . , . , F (x +D x) >0, F (x)<0,
F (x +D x)+ F (x)= Ss (x +D x) - Ss (x)= , (32)
, D (. .11)! , s e , , Þ e >0, Þ s >0! (32) (31) S D x;
, (33)
.. , Þ :
(34)
, G .
. . (.12) F F. : ; , .. α . ≈ , .. ≈ . ( ) l, ldx × = F dx,
. (35)
,
(36)
. (33), , , . , . . , D >0,Þ , Þ , Þ D x <0, .. D D x :
.
,
, Þ , Þ . (37)
, Þ rV =const, (r - ) Þ dr×V+r×dV= 0, dr/r =- dV/V. , (34) . (38)
|
|
, ( ) : pV g=const. : , Þ (37), Þ , Þ , -
. (38), . (- , ? : i?)
. () , : F=mx, m - . Fdx=mxdx 0 . = . , Þ ()
U = . (40)