第十一章 质点运动微分方程.ppt

Part 3: Dynamics
Theoretical Mechanics
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第三篇《动力学》
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Dynamics
Introduction
1. The subject of dynamics is the relation between the mechanical motion of a material body and the force acting on it.
2. Two models of mechanics.
1) A particle is a material body possessing mass, the shape and size of which can be neglected in investigating its motion.
Examples: When we study a satellite’s orbit the satellite may be regarded as a particle. ,satellite particle.
A rigid body in translation motion
can always be treated as a particle.
,rigid body particle.
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.
A rigid body is a special system of posed 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.
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动力学
引言
:
:
研究物体的机械运动与作用力之间的关系
:由有限或无限个有着一定联系
的质点组成的系统。
:具有一定质量而不考虑其形状大小的物体。
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。
例如: 研究卫星的轨道时,卫星质点;
刚体作平动时,刚体质点。
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System of free particles: a system in which the motion of each particle is not restricted by any constraints.
System of non-free particles refers to a system in which the motion of particle is restricted by constraints.
A system of particles is the most general abstract model of mechanics including rigid bodies, elastic bodies and fluids.
3. Classification of dynamics:
Particles dynamics Particle dynamics is the basis of the
Dynamics of a system of particles dynamics of a system of particles
4. The fundamental problems of dynamics:
There are two cases in general. One is to determine the acting forces when the condition of motion is known, the other is to determine the motion of the body when the acting forces are known.
There are still some prehensive problems. Sometimes part of the forces and part of the motion are known, we