理论力学中英文第一章PPT课件.ppt

4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University1 1静力学引言静力学引言Introduction to Statics. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University2 2静力学静力学 Statics ：静力学是研究物体的受力分析、静力学是研究物体的受力分析、力系的等效替换（或简化）、力系的等效替换（或简化）、Statics is defined as a subject which study the force analysis, reduction of force system建立各种力系的平衡条件的科学建立各种力系的平衡条件的科学and establish the equilibrium equations of various force system. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University3 31、物体的受力分析： Force Analysis分析物体（包括物体系）受哪些力，每个力的作用位置和方向，分析物体（包括物体系）受哪些力，每个力的作用位置和方向，并画出物体的受力图并画出物体的受力图Analyze the forces acting on the body, and identify the magnitude, direction and active point of the forces draw a Free-body diagram.2、力系的等效替换（或简化）：、力系的等效替换（或简化）： Reduction of force system用一个简单力系等效代替一个复杂力系。

用一个简单力系等效代替一个复杂力系 A complex force system is replaced by a simple one. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University4 43、建立各种力系的平衡条件：、建立各种力系的平衡条件：Establish the equilibrium equations of various force system建立各种力系的平衡条件，并应用这些条件解决静力学实际问题建立各种力系的平衡条件，并应用这些条件解决静力学实际问题 Practical problems is solved by using the established equilibrium equations.几个基本概念：几个基本概念： Fundamental Concepts刚体：刚体：Rigid body在力的作用下，其内部任意两点间的距离始终保持不变的物体在力的作用下，其内部任意两点间的距离始终保持不变的物体. A rigid body is a combination of a large number of particles occupying fixed positions with respect to each other. . .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University5 5力力 Force 物体间相互的机械作用，作用效果使物体的机械运动状态发生物体间相互的机械作用，作用效果使物体的机械运动状态发生改变。

改变A force represents the mechanical action of one body on another. The mechanical motion state of the body can be changed by it.力的内效应和力的外效应：力的内效应和力的外效应：The effect of action of the force consists of internal effect and external effect.力的三要素：大小、方向、作用点力是矢量力的三要素：大小、方向、作用点力是矢量Three factors of forces are defined as magnitude, direction and point of application. Forces are vectors. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University6 6力系力系 Force system一群力可分为：平面汇交（共点）力系；平面平行力系；平面力一群力可分为：平面汇交（共点）力系；平面平行力系；平面力偶系；平面任意力系；空间汇交（共点）力系；空间平行力系；偶系；平面任意力系；空间汇交（共点）力系；空间平行力系；空间力偶系；空间任意力系。

空间力偶系；空间任意力系 Force system is defined as a group of forces which act on the same body. Classification of force system Coplanar force system can be classified as coplanar concurrent force system, coplanar parallel force system,coplanar force-couple system and general coplanar force system. Forces in space can be classified as spatial concurrent force system, spatial parallel force system, spatial force-couple system, general spatial force system. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University7 7平衡平衡Equilibrium 物体相对惯性参考系（如地面）静止或作匀速直线运动。

物体相对惯性参考系（如地面）静止或作匀速直线运动 The body is in equilibrium if it remains at rest or moves with a constant speed in a straight line relative to the inertial reference frame. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University8 8第一章第一章 静力学公理和物体的受力分析静力学公理和物体的受力分析 Chapter 1 Axioms of Statics and Free-body Diagram1-1 静力学公理静力学公理Section 1.1 Axioms of Statics. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University9 9公理公理1 力的平行四边形法则力的平行四边形法则Axiom 1 The parallelogram law作用在物体上同一点的两个力，可以合成为一个合力作用在物体上同一点的两个力，可以合成为一个合力 Two forces acting on the same point of a body can be replaced by a resultant force合力的作用点也在该点，合力的大小和方向，由这两个合力的作用点也在该点，合力的大小和方向，由这两个力为边构成的平行四边形的对角线确定，如图所示。

力为边构成的平行四边形的对角线确定，如图所示 . The resultant force can be obtained by constructing a parallelogram, using the two forces as two adjacent sides of the parallelogram. The diagonal that passes through the point of application of two forces represents the magnitude and direction of the resultant force. . .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University1010合力合力(合力的大小与方向合力的大小与方向) (矢量的和矢量的和) Resultant force (the magnitude and direction of the resultant force) (the vector sum)亦可用力三角形求得合力矢亦可用力三角形求得合力矢Resultant force also can be determined by force triangle rule. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University1111 公理公理2 二力平衡条件二力平衡条件 Axiom 2 Equilibrium conditions of two forces 作用在刚体上的两个力，使刚体保持平衡的必要和充分条件是：作用在刚体上的两个力，使刚体保持平衡的必要和充分条件是：这两个力的大小相等，方向相反，且作用在同一直线上。

这两个力的大小相等，方向相反，且作用在同一直线上The sufficient and necessary equilibrium conditions of two forces acting on a rigid body arethat the two forces have the same magnitude and the same line of action but opposite sense. .4/10/20224/10/20224/10/2022Nanchang Hangkong UniversityNanchang Hangkong University1212公理公理3 加减平衡力系原理加减平衡力系原理Axiom 3 The principle of addition and subtraction of equilibrium force system在已知力系上加上或减去任意的平衡力系，并不改变原力系在已知力系上加上或减去任意的平衡力系，并不改变原力系对刚体的作用对刚体的作用The rigid body will remain unchanged if a equilibrium force system is added or subtracted from the original force system acting on the rigid body. .4/10/20224/10/20224/10/2022Nanchang Hangkong Univ。