:
d () = .
, .
d () = Fx d x + Fy d y + Fz d z.
, , (. 2.7) , d ()= Fx d x. Fx = - F, x = BC cosj d x = - BC sinj dj,
d() = F BC sinj dj.
, l = Oz, , l=Oz,
d () = l=Oz dj,
dj - l =Oz.
d () = F t d s,
F t , d s .
d () = Fv d S,
Fv , d S .
d = d U d = - d.
, , .
, ( ).
.
, , , . , , f (x, y, z)= 0, ,l .
, , , ,
.
:
1. () . d ()= × = | | × | |cos () = 0, , , .
2. . , d ()= × = 0.
3. , . -
(. 2.8), . d ()= × = 0 .
4. . . , . , (. . 2.1).
|
|
, , , . , ,
. (2.12)
h s = 3 n - h , (i = s) (2.11), k-
; .
(2.12),
. (2.13)
(2.14)
, i - .
(2.14) (2.13),
. (2.15)
, i - , , .
, , ( , Tj Nj (Tj , , , ).
, . , , . , , , .
2.10. r m, (. 2.9), : q = s - , q = j - . , Qs = mg sina, - Q j = mg r sina.
. (2.15) , , . q q = s - ,
Qs . q = j ( ), Q j ´.
.
1. (2.14),
= .
, ,
. (2.16)
.
2.11. Qq= j, - (. 2.10) OA=AB= l, , .
. F 1 x= 0 F 2 y= 0, (2.16)
.
F 1 y=- F 1; F 2 x=- F 2; yA = l sinj; xB = 2 l cosj. , Qq= j= - F 1 l cosj + 2 F 2 l sinj.
|
|
. 2.10
2. . s=k > 1 , , , , . , , . (2.15)
. (2.17)
qi (2.17) , , , , i- .
2.12. (. 2.11). 1 m 1, 2 m 2, r. 3 2 . 2 .
. - d s ¹ 0 1, j 2, j =const,.. dj =0. 2 , . ,
,
P 1 =m 1 g; P 2 =m 2 g.
, , d s= 0,dj ¹ 0.
.
3. , , , U .
(2.17),
U = - ,
(2.18)
2.13. , . 2.12, 1 2 m 1 m 2, r, 1 .
. 2.12
, , , , s =0 .
.
.
, :