Theoretical mechanics Review o part i statics
1 Theoretical Mechanics
理论力学 静力学复习
2
Statics Review of statics 1. The basic concepts and the difference between them (The difference between a resultant R and the principal vector R: Resultant force R is the sum of the translational effect of the principal vector and the rotational effect of the principal moment(principal vector and principal moment reduce to a resultant force). (It depends on the point of application Principal vector R'only causes only a translational effect Additionally a principal moment may exist. (it does not depend on the point of application 2The difference between a force moment and a force couple moment Force moment is the moment of a force about a point, it depends on the center point. Thereby, it can not be transferred arbitrarily in a plane an Force couple moment can be transfered freely in the plane or in another plane which is parallel to the plane. It does not depend on the center point
3 1. The basic concepts and the difference between them: ①The difference between a resultant R and the principal vector R'. Resultant force R is the sum of the translational effect of the principal vector and the rotational effect of the principal moment (principal vector and principal moment reduce to a resultant force). (It depends on the point of application) Principal vector R' only causes only a translational effect. Additionally a principal moment may exist. (it does not depend on the point of application) ②The difference between a force moment and a force couple moment Force moment is the moment of a force about a point, it depends on the center point. Thereby, it can not be transferred arbitrarily in a plane. Force couple moment can be transfered freely in the plane or in another plane which is parallel to the plane. It does not depend on the center point. Review of Statics
学 静力学复习 基本概念及概念的区分 ①合力R和主矢R的区别 合力R:是主矢的移动效果和主矩转动效果之和(主矢,主矩可 j化为合力)。(与作用点有关) 主矢R:只代表移动效果,且有主矩存在时(与作用点无关) ②力矩和力偶矩的区别 力矩:是力对那一点的转矩,与取矩点有关,且不能在平面内 任意移动。 力偶矩:它是在平面内和平行它自身平面内可任意移动,与取矩 点无关
4 一. 基本概念及概念的区分 ① 合力R 和主矢 R' 的区别 合力R : 是主矢的移动效果和主矩转动效果之和 (主矢,主矩可 简化为合力)。 (与作用点有关) 主矢R': 只代表移动效果，且有主矩存在时(与作用点无关) ② 力矩和力偶矩的区别： 力矩:是力对那一点的转矩, 与取矩点有关, 且不能在平面内 任意移动。 力偶矩: 它是在平面内和平行它自身平面内可任意移动,与取矩 点无关。 静力学复习
Statics @The invariants of the reduction of a general coplanar force system to RER R a given center The invariants of the reduction of a general force system in space to a given center are R in a plane: R In space: R ,=(RR (4) The way to judge the direction of the force of friction Force of friction is a sort of constraint reaction force Its direction is always opposite to the relative motion of the bodies
5 ③The invariants of the reduction of a general coplanar force system to a given center. The invariants of the reduction of a general force system in space to a given center are in a plane: in space: R' // R' ; M M =(R R) ⊥ , ④ The way to judge the direction of the force of friction: Force of Friction is a sort of constraint reaction force. Its direction is always opposite to the relative motion of the bodies.