. . , Ox (. 3.4, ). c x P = cx, F = - P (. 3.4, ).
, , .
P :
A (P) = Pdx = cxdx = cx 2/2 = Px /2.
, :
A (P) = Px /2. (3.5)
F |
. 3.4
, , F = - P : A (F) = - A (P).
W, A . A = - W.
. i j (. 3.5, ).
. 3.5
i , Pi , , , . 3.5, . D ii D ji i j, Pi.
Pi j Pj. i D ij, j D jj (. 3.5, ).
, :
A (Pi) =1/2 Pi D ii + Pi D ij; (3.6)
A (Pj) =1/2 Pj D jj. (3.7)
, Pi , , (3.6) (3.5). Pi = const (3.3).
, Pi D ij, Pj, 1/2.
1. , , D i ( vi), q i , Pi Mi, (3.6) :
A (Mi) = 1/2 Mi q ii + Mi q ij,
q ii i, Mi, q ij i, Pj.
2. , : ui, vi, q i 1.11 1.3. D i, , , . D i : P M . .
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3. , , , , .