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,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,高等教育出版社出版,Physics deals with matter,motion,and their interaction.,Physics deals with matter,1,Im Walter Lewin.,I will be your lecturer this term.,In physics,we explore the very small,to the very large.,The very small is a small fraction of a proton,and the very large is the universe itself.,They span 45 orders of magnitude-,a 1 with 45 zeroes.,*,Im Walter Lewin.I will be you,2,MECHANICS,（力学）,:,Kinematics,（运动学）,Dynamics,（动力学）,MECHANICS（力学）:Kine,3,Chapter 2&3,Motion in One,Two and Three Dimensions,（一维，二维和三维运动）,2-1 Description of motion,（运动描述）,A,coordinate system,(坐标系),is built on it.,x,y,O,z,Particle,(质点):,Relativity of description of motion,(,运动描述的相对性),Absoluteness of motion,(,运动的绝对性),Reference Frame,(参照系),should be chosen,.,an idealized model,(理想模型P12),Chapter 2&3 2-1 Descriptio,4,2-2.,Position and Displacement,(位置和位移）,1.,Position Vector,(位矢）,The position vector extends from the origin of a coordinate system to the particle（从坐标原点到质点）.,x,y,r(,t,),In,rectangular coordinate system,(,直角坐标系),:,Motion Function,(,运动方程),：,Its three components,(三个分量）,are written by the following scalar functions,（写为下列标量方程）,The,Trajectory,equation,(,轨道方程,),can be obtained by eliminating,t,from these equations,（可从这些方程中消去,t,得出),i,k,j,P,z,(,t,0,),(,t,),z,x,y,O,2-2.Position and Displacemen,5,2,.,Displacement,(,位移,),y,x,0,r,1,(,t,),A,B,z,r,2,(,t+,t,),r,Displacement,depends,only,on the position of initial point and final point,(i).,The,magnitude,of vector,（矢量的量值）,should be the,length,of this vector,（应为该矢量长度),i.e.,(ii),.,Different from the path,(路程),Path,is the,total,length of the trajectory curve.,Its a,vector,.,Its a,scalar,.,independent with the real path.,2.Displacement (位移)yx0r1,6,In the limit as,t,0,（当,t,0时极限下）,r,(,t,+,t,),r,(,t,),0,r,r,?,Hey!,x,r,(,t,+,t,),r,(,t,),y,z,P,2,P,1,0,S,In the limit as t 0,r(t+t),7,2-3.Average Velocity and Instantaneous Velocity,1.,Average,velocity,(平均速度):,2.,Instantaneous,velocity,(,瞬时速度),:,Velocity is the(first)derivative of position vector with respect to time,（速度是位矢对时间的一阶导数）.,y,x,0,r,1,(,t,),A,B,z,r,2,(,t+,t,),r,2-3.Average Velocity and Ins,8,3.Average and Instantaneous,Speed,The magnitude of velocity equals speed,(,速度的量值等于速率),:,Average Speed:,（,平均速率）,Instantaneous Speed:,（瞬时速率）,Note:,Speed,:,Average Speed:,（,平均速率）,3.Average and Instantaneous S,9,2-4.Average and Instantaneous Acceleration,Average,Acceleration:,(平均加速度):,Instantaneous,Acceleration:,(瞬时加速度),v,v,(,t,),v,(,t,+,t,),x,r,(,t,+,t,),r,(,t,),y,z,P,2,P,1,0,v,(,t,),v,(,t,+,t,),Acceleration is the time derivative of velocity.,It is the second derivative of position vector with respect to time,2-4.Average and Instantaneou,10,The component form in,Cartesian,coordinate is:,（笛卡尔坐标分量式）,Direction of :,Magnitude of :,The component form in Cartesi,11,Example 1:,o,x,y,P,The motion function for a particle is,Find:,(1),its real distance during,t,=0,to,2s,(2),Its,at,t,=2s,Example 1:oxyPThe motion funct,12,(2),(1),Real Distance,(路程）,:,It is a constant,and along,y,direction,Solution:,(2)(1)Real Distance(路程）:,13,例二,质点以加速度,a,在,x,轴上运动,初速,v,0,处在,x=x,0,位置.求任意时刻速度和位置。,解：一维运动，去掉矢量符：,两边积分,得,即,例二 质点以加速度 a 在 x 轴上运动,初速 v0,14,同理,两边积分,得,即,匀变速直线运动：,有,同理两边积分得即匀变速直线运动：有,15,Questions,(思考题）,P,36,4;,P,68,10,Problems,(练习题）,P,40,46;,P,41,67;,P,72,58,Next Lecture:Curvilinear motion,Questions(思考题）,16,
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