理论力学质点运动的微分方程11.ppt

1 因此脱离地球引力而一去不返 时（　　　）的最小初速度 （第二宇宙速度） The minimum velocity for the rocket to escape the earth’s gravitational force and to proceed infinitely away from the earth ( ) is: (the second escape velocity) * Theoretical Mechanics Introduction 引 言 刚体作平动时,刚体 质点。 A rigid body in translation motion can always be treated as a particle.I.e,rigid body particle. Examples: When we study a satellite’s orbit the satellite may be regarded as a particle. I.e,satellite particle. 例如： 研究卫星的轨道时，卫星 质点； 二.力学模型： 2. Two models of mechanics. 一.研究对象： 研究物体的机械运动与作用力之间的关系 The subject of dynamics is the relation between the mechanical motion of a material body and the force acting on it. 1.质点：具有一定质量而不考虑其形状大小的物体。 1) A particle is a material body possessing mass, the shape and size of which can be neglected in investigating its motion. 2) A system of particles is a collection of material points in which the position and motion of each particle of the system depends on the position and motion of all the other particles. 2.质点系：由有限或无限个有着一定联系的质点组成的系统。 A rigid body is a special system of particles composed of a large number of particles, the distance between any two points of which remains the same during the whole motion. It is also called to be a non-deformable system. 刚体是一个特殊的质点系，由无数个相互间保持距离 不变的质点组成。又称为不变质点系。 System of free particles: a system in which the motion of each particle is not restricted by any constraints. 自由质点系：质点系中各质点的运动不受约束的限制。 System of non-free particles refers to a system in which the motion of particle is restricted by constraints. 非自由质点系：质点系中的质点的运动受到约束的限制。 A system of particles is the most general abstract model of mechanics including rigid bodies, elastic bodies and fluids. 质点系是力学中最普遍的抽象化模型；包括刚体,弹性体,流体。 三.动力学分类: 质点动力学 质点系动力学 质点动力学是质点系动力学的基础。 3. Classification of dynamics: Particles dynamics Particle dynamics is the basis of the Dynamics of a system of particles dynami