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# 第 3 章 空间力系 - PowerPoint PPT Presentation

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## PowerPoint Slideshow about ' 第 3 章 空间力系' - carly-booker

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1.力在空间直角坐标轴上的投影

z

Fz

F

y

β

o

Fy

Fx

x

z

Fz

F

y

o

Fy

Fx

Fxy

x

2.力对轴之矩

b

y

O

= Fx• b + Fy• a

Fx

Fxy

a

d

A

Fy

x

2.力对轴之矩
• 合力矩定理 ：如一空间力系由F1、F2、…、Fn组成，其合力为FR，则合力FR对某轴之矩等于各分力对同一轴之矩的代数和。
3.空间力系的平衡
• 空间力系的简化：与平面任意力系的简化方法一样，空间力系也可以简化为一个主矢和一个主矩。
• 空间力系的平衡方程
• 平衡的必要与充分条件：
• ＝０， ＝０
3.空间力系平衡问题的平面解法

z

FBV

A

FAV

MT

B

D

y

FAH

Fr

FBH

x

FT

L/2

L/2

L1

z

xz面:

FBV

FAV

x

MT

FAH

FBH

Fr

FT

yz面:

z

FAV

FBV

y

Fr

xy面:

y

FT

FBH

FAH

x