文档介绍：Chapter 5: Force System in Space
Theoretical Mechanics
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第五章空间力系
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Practically, there exists many force systems in which the action lines of the forces are not coplanar, these are force systems in space. They are the most general force systems.
Diagram (a) is a concurrent forces system in space.
Diagram (b) is an arbitrary force system in space, if neglecting the forces of the wind from the side it is a parallel force system in space.
The force of wind from
the front
The force of wind from the side
b
Statics
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静力学
工程中常常存在着很多各力的作用线不在同一平面内的力系,即空间力系,空间力系是最一般的力系。
(a)图为空间汇交力系;(b)图为空间任意力系;
(b)图中去了风力为空间平行力系。
迎面风力
侧面风力
b
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Chapter 5: Force system in space
§5–1 Concurrent force system in space
§5–2 System of force couples in space
§5–3 The moment of a force about a point or an axis
§5–4 Reduction of a force system in space to a given
point
§5–5 Discussion of the result of the reduction of a
force system in space
§5–6 Equilibrium equations of a force system in
space and their applications
§5–7 The center of a system of parallel forces and the
center of gravity of an object
Class of exercises
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第五章空间力系
§5–1 空间汇交力系
§5–2 空间力偶系
§5–3 力对点的矩与力对轴的矩
§5–4 空间一般力系向一点的简化
§5–5 空间一般力系简化结果的讨论
§5–6 空间一般力系的平衡方程及应用
§5–7 平行力系的中心与物体的重心
习题课
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§5-1 Concurrent force system in space
1. The projection and position of a force on the axes in space:
(1)The representation of force in space:
a force is given by its
magnitude, its direction and its
point (line) of application
magnitude:
point of application: the point at
which the force acts onto the object.
direction: it can be determined by the three angles , , g or by the angle of inclination and the angle of depression .
b
g
q
Fxy
O
Statics
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静力学
一、力在空间轴上的投影与分解:
:
力的三要素:
大小、方向、作用点(线)
大小:
作用点:在物体的哪点就是哪点
方向:
由、、g三个方向角确定
由仰角与俯角来确定。
b
g
q
Fxy
O
§5-1 空间汇交力系
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(2) The method of direct projection
From the fig we see
(3) The method of indirect projection When t