1970年代以来,经济全球化进程一直在加速, 具体表现为贸易的大幅度增长和国际间金融交 易大幅度增长。中国已经成为WT0的成员国, 这使得中国会以一个渐进的,但逐步加快的方 式逐步融入世界经济。虽然在过去的20年里 中国的出口一直高速增长,但目前中国的企业 和产业部门在世界市场上所面对的竞争是严峻 的,未来一段时间内,这种严峻的形势将继续存 在。由于大量外国企业进入中国,和大量外国 产品进入中国市场,中国的企业和产业部门在 中国国内市场也面对严峻的国际竞争

CSA是剑桥科学文摘(Cambridge Scientific Abstracts)的简称。它由美国一家著名的私 人信息公司编辑出版,该公司出版科学技术研究文献的文摘和索引工具已有30多年的历 史。目前,CSA通过因特网可提供70多个数据库的检索服务。内容范围包括:生命科 学、环境与水科学、计算机科学、材料科学与工程、航空航天以及人文社会科学

We will start by studying the motion of a particle. We think of particle as a body which has mass, but has negligible dimensions. Treating bodies as particles is, of course, an idealization which involves an approximation. This approximation may be perfectly acceptable in some situations and not adequate in some other cases. For instance, if we want to study the motion of planets it is common to consider each planet as a particle

In this lecture we will look at some other common systems of coordinates. We will present polar coordinates in two dimensions and cylindrical and spherical coordinates in three dimensions. We shall see that these systems are particularly useful for certain classes of problems Like in the case of intrinsic coordinates presented in the previous lecture, the reference frame changes from point to point. However, for the coordinate systems to be presented below, the reference frame depends only on the position of the particle. This is in contrast with the intrinsic coordinates, where the reference frame is a function of the position, as well as the path

In this lecture we will look at some applications of Newton's second law, expressed in the different coordinate systems that were introduced in lectures D3-D5. Recall that Newton's second law F=ma, (1) is a vector equation which is valid for inertial observers. In general, we will be interested in determining the motion of a particle given

In this lecture we will consider the equations that result from integrating Newtons second law, F=ma, in time. This will lead to the principle of linear impulse and momentum. This principle is very useful when solving problems in which we are interested in determining the global effect of a force acting on a particle over a time interval Linear momentum We consider the curvilinear motion of a particle of mass, m, under the influence of a force F. Assuming that

So far we have used Newton's second law= ma to establish the instantaneous relation between the sum of the forces acting on a particle and the acceleration of that particle. Once the acceleration is known,the velocity (or position) is obtained by integrating the expression of the acceleration (or velocity). There are two situations in which the cumulative effects of unbalanced forces acting on a particle are of interest to us. These involve:

In the previous lecture, we related the motion experienced by two observers in relative translational motion with respect to each other. In this lecture we will extend this relation to our third type of observer.That is, observers who accelerate and rotate with respect to each other. As a matter of illustration, let us consider a very simple situation, in which a particle at rest with respect

Inertial reference frames In the previous lecture, we derived an expression that related the accelerations observed using two reference frames, A and B, which are in relative motion with respect to each other. aA =aB+(aA/ B)'y'' 22 x (DA/ B) 'y'2'+ TA/B+ X TA/B). (1) Here, aA is the acceleration of particle A observed by one observer, and

In this lecture, we will start from the general relative motion concepts introduced in lectures D11 and D12. and then apply them to describe the motion of 2D rigid bodies. We will think of a rigid body as a system of particles in which the distance between any two particles stays constant. The term 2-dimensional implies that particles move in parallel planes. This includes, for instance, a planar body moving within its plane