1.
- , () N ( ); .
.
- ( ) Z , : N = S (F 
).
N :
, () ( 1.1, );
, () ( 1.1, ).
1.1.
1.1. ( 1.2, ) .
. .
, .
, ( 1.2, ). .
z - .
, . , z .
, N. , . . ().
N ( 1.2, , , ).
, zi:
1.2.
I (0 < z 1 < ℓ)
Σ FZ = F NI = 0; Þ NI = F;
II (0 < z 2 < ℓ)
Σ FZ = F 3F NII = 0; Þ NII = F 3F = 2F;
III (0 < z 3 < 2ℓ)
Σ FZ = F 3F +5F NIII = 0; Þ NIII = F 3F +5F = 3F.
, I III , .
, II , , , . . .
: N , N zi.
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( 1.2, ).
: N . , .
2.
, , . .
, , ; , , .
- ( ) z , : = Σ mZ (F ).
( 1.3, , ):
1.3.
, .
, .
1.2. , 1.4.
. . .
1.4.
I : = 4m,
II : = 4m 5m = m,
III : = 4m 5m + 2 m = m.
. , .
, .
3 4.
, . , .
Q .
Q :
, , ( 1.5, ). , , Q ;
, , ( 1.5, ), . . Q , .
1.5
:
, ( 1.6, ), . . ;
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, ( 1.6, ), . . .
1.6
, .
: , ; .
Qy ( ) , , , :
Q = Σ (F 
).
( ) , , , :
= Σ m (F 
).
1.3. Qy , 1.7, .
1. :
Σm = 0, Fℓ + 3ℓ 2F 4ℓ = 0 Þ = 3F,
Σm = 0, 2Fℓ Fℓ 3ℓ = 0 Þ = F,
Σ FΖ = 0, ΖΑ = 0.
:
Σ F = F + 3F 2F = 0 .
2. Q. . . , Q ( 1.7, ).
Ι : Q = F.
( 1.7, ).
ΙΙ : Q = F+ 3F = +2F.
, .
Q ( 1.7, ). Q .
1.7.
3. .
, , , :
= Fℓ ( ),
= Fℓ F ∙ 3ℓ = 2Fℓ ( ).
, Fℓ - 2 Fℓ.
= Fℓ F ∙ 4ℓ + 3Fℓ = 0.
( 1.7, ).
.
