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 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

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 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

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

密立根(Bobert Andrew Millikan)1868年3月22日生 于美国伊利诺斯州的莫里森镇他的父亲是镇上的牧师。 他生活和工作在一个以物理学最富革命性的发展为其特 征的时期,在这段时期建立的许多概念构成了我们今天 物理观念的基础。 密立根设计了一种研究油滴在电场和重力场作用下 运动的方法。这一实验后来被称做油滴实验,比起较早的 方法这是一项重大改进,用它得到了可靠并且可以重复测 量的电子电荷值。密立根令人信服地证明了电荷的不连续 性,这对最终建立物质的原子论有着重大的作用

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一、青金石和方钠石 青金石也是一种古老的玉石,已有五、六千年的使用历史了。 它美丽的湛蓝色和金光闪闪的“金星”交相辉映,备受人们 青睐。它和绿松石一样,在古老的文明中就颇为人们喜爱。 普林尼(Pliny)曾这样描写过“蓝宝石”:“蓝宝石(Sapphire) 含有金子般的斑点。它有时呈蓝色,虽然有时也染了紫色 的蓝色,但实际上稀少

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