理论力学-绪论

1、理 论 力 学绪 论概 要 1.1 力学发展简史 1.2 牛顿力学，工程力学 力学概念复习TheBigPicture 回顾力学发展史及形成现代工程力学基础的一些基本概念 介绍有助于工程师职业生涯的解决问题的方法1.1 力学发展简史目的 定义力学科学并简述其发展史 识别并区分质点系与刚体系统Key Concepts力学是研究物体在力作用下运动的科学。静力学研究静止的或以匀速运动的系统。1.1 力学发展简史Archimedes ( 287_212 B.C. )平行力分析法则Principles for the Analysis of Parallel Forces1.1 力学发展简史Archime

2、des ( 287_212 B.C. )ApplicationSimple Levers ( 杠杆）Systems of pulleys（滑轮系统） Floating bodies (浮体）Centers of gravity of bodies (重心）1.1 力学发展简史平行力分析法则Principles for the Analysis of Parallel ForcesSimon Stevin (1548_ 1602 )力的平行四边形法则Principles of Force Parallelogram虚功原理The Principles of Virtual Work1.1 力学发

3、展简史Simon Stevin (1548_ 1602 )Inclined plane problem1.1 力学发展简史力的平行四边形法则Principles of Force ParallelogramFig. 1.1 有向线段 Directed line segment2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Segment 线段上任意两点之间的部分1.1 力学发展简史Fig. 1.2 力的平行四边形 Fo

4、rce parallelogram2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Parallelogram 平行四边形法则Resultant 合矢量，合成的1.1 力学发展简史Rene Descartes ( 1549_ 1650 )Resolving vectors into projectionsParallel to coordinate axes1.1 力学发展简史Aristotle ( 384_322 B.

5、C. )亚里斯多德的理论中存在一些错误的结论There are some erroneous conclusions in Aristotelian theory 由于错误地认为力是维持运动的必要因素due to false belief that force was necessary to maintain motion.1.1 力学发展简史Aristotle ( 384_322 B.C. )错误之一： 认为在引力场中，重的物体比轻的物体下落更快One of them is that in a gravity field heavy bodies fall faster than ligh

6、t bodies do1.1 力学发展简史Galileo ( 1564_1642 )通过试验和分析，伽俐略以他对动力学的特殊贡献奠定了动力学作为一门科学的基础By experiments and analysis,Galileo laid the foundationfor the science of dynamics,with his particular contribution to kinetics1.1 力学发展简史Tower PisaNicolaus Copernicus ( 1473_1543 )日心说Heliocentric UniverseOn the Revolution

7、s of the Celestial Spheres 挑战了2000千年来从未被质疑过的亚里斯多德的地心宇宙论Challenged Aristotelian Geocentric Universethat had never been questioned for 2000 years 1.1 力学发展简史By observing the behaviors of Venusand careful calculationbased on it, naturally Copernicus concluded that instead of the earthit is the sun that

8、lies as the centre of the planetsIssac Newton ( 1642_1727 )万有引力定律The Law of Universal Gravitation牛顿三大定律The Three Laws of Motion1.1 力学发展简史Issac Newton ( 1642_1727 )1.1 力学发展简史Newton Bridge in Cambridge1.1 力学发展简史Newton Bridge in Cambridge1.1 力学发展简史Apple Tree1.1 力学发展简史Albert Einstein ( 1879_1955 )狭义相对论S

9、pecial Relativity广义相对论General Relativity1.1 力学发展简史1.1 Brief History of MechanicsAlbert Einstein ( 1879_1955 )银河系 Galaxy1.1 Brief History of MechanicsAlbert Einstein ( 1879_1955 )银河系中心 Core of Galaxy1.1 Brief History of MechanicsAlbert Einstein ( 1879_1955 )1.1 Brief History of MechanicsAlbert Einste

10、in ( 1879_1955 )Hubble Space Telescope哈 勃 望 远 镜1.1 Brief History of MechanicsAlbert Einstein ( 1879_1955 )Hubble Space Telescope相对论量子论的理论表明当物体运动接近光速或当研究亚原子运动时，牛顿力学是不精确的The theories of relativity and quantum show that Newtonian mechanics is inexact when speeds approach the speed of light or the motio

11、n of subatomic particles is considered.1.1 力学发展简史然而除上述情况以外，牛顿力学在所有其它情况下都是准确的, 因而奠定了解决绝大多数现代工程问题的基础。However, Newtonian mechanics is precise for all other cases, and forms the basis for the analysis of the vast majority of modern engineering problems.1.1 力学发展简史1.1 力学发展简史现代工程问题 Modern Engineering Probl

12、ems现代工程问题 Modern Engineering ProblemsBrooklyn Bridge现代工程问题 Modern Engineering ProblemsFunctional Bridge现代工程问题 Modern Engineering ProblemsForces Transferring Along the Cable现代工程问题 Modern Engineering ProblemsForces Transferring Along the Cable现代工程问题 Modern Engineering ProblemsProcess Building A Cable

13、Bridge 现代工程问题 Modern Engineering ProblemsHow to Make Cables例1. 吊桥的绳索支承 A,B 两立柱间均质路面的一半重量。若 此载荷为 wo，求绳索的最大张力和整根绳索需要的长度。 跨度 L 和垂度 h 已知现代工程问题 Modern Engineering Problems.Panama Canal现代工程问题 Modern Engineering Problems.Panama Canal现代工程问题 Modern Engineering ProblemsPassing Though A Canal例2. 液压油缸推动活塞从而带动连杆

14、关闭水闸。矩形门宽2米。 当水深h达3米时，计算推动油缸活塞所需油压。 活塞直径为150毫米。Hovercraft现代工程问题 Modern Engineering ProblemsAircraft Carrier现代工程问题 Modern Engineering ProblemsExploring Ocean现代工程问题 Modern Engineering Problems例3. 一电缆船拖动犁头A勘察海床，以便铺设海底电缆。电缆船均匀 低速行驶，犁头A位于水下600英尺，同时缆绳留有足够长度以便 能够水平牵引犁头A。船尾到犁头的水平距离为1600英尺，缆绳重 为3.10磅/英尺。计算作用

15、于犁头的水平牵引力To，缆绳最大张力 以及缆绳的长度（AB)。Manipulator现代工程问题 Modern Engineering Problems例4. 深海潜水器潜水舱直径为1500 mm, 配以铅质压舱物，以使其自重 略微超过浮力的的大小。当潜水舱潜入水下3km 时，舱内维持大 气压。潜水舱壳体厚为 25 mm，试计算作用于直径横截面上的压 应力。现代工程问题 Modern Engineering ProblemsManipulator现代工程问题 Modern Engineering ProblemsEarthquake Wave Monitoring现代工程问题 Modern E

16、ngineering ProblemsEarthquake Monitor现代工程问题 Modern Engineering ProblemsApplication ofBiomechanics现代工程问题 Modern Engineering ProblemsArtificialAcetabulum 现代工程问题 Modern Engineering ProblemsArtificial Wrist 现代工程问题 Modern Engineering Problems例5. 10 kg 重的石头握在手中，求肱骨 H 和二头 肌 B 给桡骨 C 和尺骨 A 施加的力。Key ConceptsA

17、 particle is a body whose size does not influence its response to the forces acting on itObjects for study of mechanics质点 PARTICLE1.1 力学发展简史Key ConceptsA rigid body is a body that does not deform under the action of forces. Generally, the size of a rigid body influences its response to forces.Rigid

18、刚体 Deform 使变形Objects for study of mechanicsRIGID1.1 力学发展简史Key ConceptsThe acceleration of a particle is proportional to the net force that acts on the particle and inversely proportional to the mass of the particle.Acceleration 加速度Proportional 成比例的Inversely 相反地Net 净余的1.2 牛顿力学，工程力学NEWTONS LAWS OF MOT

19、IONKey ConceptsEvery force (action) is accompanied by an equal and opposite force (reaction).NEWTONS LAWS OF MOTION1.2 牛顿力学，工程力学Fig. 1.3 Original definition of the meter.2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.1.2 牛顿力学，工程力学Key

20、ConceptsWeight is a force, not a mass. The kilogram is a unit of mass, not a unit of weight.1.2 牛顿力学，工程力学Fig. 1.4 Balance-type scale.2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Scale 天平，比例尺， 刻度，衡量1.2 牛顿力学，工程力学Fig. 1.5 Spring scale:

21、 (a) in a zero-gravity field; (b) on the moon; (c) on earth.2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.Fig. 1.6 A force of 1 N acting on a mass of 1 kg produces an acceleration of 1 m/s22001 Brooks/Cole, a division of Thomson Lear

22、ning, Inc. Thomson Learning is a trademark used herein under license.1.2 牛顿力学，工程力学Fig. 1.7 The weight of a unit mass equals g units of force.2001 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license.1.2 牛顿力学，工程力学Key ConceptsSI is an absolute system of units. The United States Customary System is a gravitational system of units.Absolute 绝对的Customary 惯例的Gravitational 重力的1.2 牛顿力学，