, , , , (4.3) (4.5) .
, . ():
() () () (5.1)
´ , . .
, (). , , , .
() , , .
() ().
, (4.3) (4.5) ?
, , :
1) ;
2) ;
3) , , ;
4) , , ;
5) , , .
5.3. Q = 600 l = 4 , h = 3 , 30. , . T - RB - RA (.5.5).
. , . , Q , = 2 .
1) , S MA = 0, RB:
- RB × + Q × (l /2) × sin30 = 0,
= h / cos30= 2 .
, :
RB ×2 = 600×2×(1/2) = 600,
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RB = 600/ (2 ) = 100 @ 173.
RA, , RB . , , (5.1). , , (4.3) (5.1):
2) S X = 0; RB × cos30 - = 0; ð = RB × cos30= 100 ×( /2) = 150 ;
3) S Y = 0, RB × sin30- Q + RA = 0; ð
RA = Q - RB ×sin30= 600 - 50 @ 513 .
, RA RB, : S MB = 0, :
RA × sin30- × cos 30 - Q × ( - l /2) × sin30= 513×2 ×(1/2) -
- 150×2 ×( /2) - 600×(2 - 2)×(1/2) = 513× - 150×3 - 600×( -1) @
@ 513×1,73 - 450 - 600×0,73 = 887,5 - 888 = - 0,5.
D = - 0,5 .
, , :
e = [½D½/min (½S+½,½S-½)]×100% =
= [½- 0,5½/min (½887,5 ½,½- 888½)]×100% = (0,5/887,5) ×100% = 0,06%.
5.4. (.5.6). , , , - .
. , , Q.
1) RB S MA = 0. , , :
RB ×2 + sin30×3 - cos30×4 = 0; ð
RB = (1/2)× Q (cos30×4 - sin30×3) = (5/4) × (4 - 3) .
2) YA S M = 0, RB A:
- YA ×2 + sin30×3 - cos30×2 = 0; ð
YA = (1/2)× Q (sin30×3 -cos30×2) = (5/4) × (3 -2 ) .
3) , A:
S X = 0; A - sin30 = 0; ð A = Q sin30 = 5/2 .
, , :
S MD = A ×3 - YA ×4 - RB ×2 = 15/2 - 5× (3 -2 ) - (5/2) × (4 - 3) =
= 15/2 - 15 + 10 -10 +15/2 = 0.
5.5. , (.5.7).
. Q 1 = 5 Q 2 = 3 , - A, YA M (.5.7).
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1) S M = 0; M - Q 1×2,5 - Q 2× 5,5 = 0; ð
M = 5 ×2,5 + 3 × 5,5 = 12,5 + 16,5 = 29 .
2) S X = 0; A + Q 1× sina = 0; ð A = - 5×(3/5) = - 3 .
3) S Y = 0; YA - Q 1 cosa - Q 2 = 0; ð YA = 5×(4/5) + 3 = 4 + 3 = 7 , sina = 3/5, cosa = 4/5.
: S M = 0; M + A ×3 - YA ×7 + Q 1 cosa×4,5 + Q 1sina×1,5 + Q 2× 1,5 =
= 29 -3×3 - 7×7 + 5×(4/5)×5 + 5×(3/5)×1,5 + 3×1,5 = 29 - 9 - 49 + 20 +4,5 +4,5 =
= 58 - 58 = 0.
:
1. , - . , 1% (. 5.3).
2. , , -, , , , . -, , : .
, , .
, ,
. , .
, . .
.
1. , 2.2, , : , BD , , , .
, : SA, SC SD - : S X = 0, S Y = 0. , .
2. , - , (.5.8).
: (4.3), (4.4) (4.5), 5 : XA, YA, MA, XB YB. .
, .
, (. 5.9). : AC BC, C. .
1 . AC, , 7 (XA, YA) (XC, YC) (. 5.9).
BC - (XB, YB) C - (XC¢, YC ¢), 5: XC = XC¢, YC = YC ¢.
, , : XA, YA, XC = XC¢, YC = YC ¢, XB , YB , .
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, 4 , , . .
2 . , XA, YA, XB , YB.
, . , , , (.5.9).
, . :
S MA = 0;
S X = 0; (5.2)
S Y = 0.
4 XA, YA, XB YB. , , : S M = 0 , . . , - . , XA, YA, XB , YB . , : S X () = 0 : - X ¢ + XB = 0 , X ¢, S M () = 0 . , :
S MA = 0; ð YB = /4;
S M = 0; ð Y = - /4;
S M () = 0; ð XB = - /4;
S X = 0; ð X = -3 /4.
: S M () = 0 , : - Y ×2 + X ×2 + ×1 = /4×2 -3 /4×2 + ×1 = /2 - 3 /2 + = 0.
, 4 : X Y - , XB YB - , .
5.6. (.5.10).
. , , . , , Q 1, - Q 2, Q 1 = Q 2 = 2.
1) RB S M () = 0: ð RB = 1;
. Q 1, Q 2 RB , R (.5.10), 5.2:
2) S M = 0; ð M = 4;
3) S Y = 0; ð R = 3.
:
S M () = M - R ×2 + Q 1×1 = 4 - 3×2 + 2×1 = 6 - 6 = 0.
5.7. (.5.11).
. :
S M = 0; M + Y ×3 - XB ×1 = 0;
S M () = 0; M + Y ×1 + XB ×1 = 0.
: XB = - M /2; Y = - M /2.
, :
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S = 0; X + XB = 0; ð X = M /2;
S Y = 0; Y + Y = 0; ð Y = M /2.
. S M () = X ×2 - Y ×2 = M - M = 0.
5.8. (.5.12).
. , . (5.9):
1) S M = 0; ð Y = /2;
2) S M () = 0; ð = - /2;
3) S M = 0; ð Y = /2;
4) S = 0; ð X = /2.
. , . , , (.5.12):
S () = 0; ð XC = /2;
S Y () = 0; ð YC = - /2.
, YC . , YC - /2.