旋转体体积的计算

用定积分计算平面图形绕该平面上一条直线(旋转轴)旋转所得旋转体体积,可以归结为两种类型。     

计算旋转体体积的一般积分公式

0引言本文首先讨论了平面曲线在直线上的投影长函数 ,平面曲线 (图形 )绕一共面直线旋转所得旋转体的体积函数 ,给出了它们的积分表示式 ,进而得出计算旋转体体积的一般积分公式。关于旋转体体积的计算问题 ,一般标准分析教材 [1,2 ] 中只讨论了平面图形绕坐标轴旋转所得旋转体的体积的积分公式 ,为了应用上的便利本文将其推广 ,给出平面图形绕任一共面直线旋转所得旋转体体积计算的一般积分公式。一般认为平面曲线是 (开 )直线段到平面内的一一的 ,双方连续的 ,在上映射的象[3] .在直线段a≤ t≤ b上引入坐标 t,在平面上引入笛卡尔直角坐标…     

空间情形下旋转体体积的计算

运用定积分中的元素法,给出了空间曲线绕空间直线旋转一周所成的旋转曲面与垂直于旋转轴的两个平面所围成的旋转体体积的计算公式:V=π(m2+n2+p2)23∫tt12{[p(y(t)-b)-n(z(t)-c)]2+[m(z(t)-c)-p(x(t)-a)]2+[n(x(t)-a)-m(y(t)-b)]2}m.x′(t)+n.y′(t)+p.z′(t)dt从而将平面图形的旋转体体积推广到了空间情形.     

用“柱壳法”求旋转体体积

对旋转体的体积，通常是取一个扁圆柱体的体积为体积微元，对于有些旋转体用这种方法计算有时比较困难，而采用“柱壳法”却较方便。定理设平面图形（如图1）绕y轴旋转所成旋转体的体积为证明在[a，b]上取小区间[x，x＋dx]以f（x）为高，dx为宽的矩形绕y轴旋转所得的圆柱形薄壳（也称柱壳）的体积的近似值2一八X）dX即为体积微元dV：推论平面图形0＜a＜x＜b，人（x）＜y＜人（x）绕y轴旋转所成旋转体的体积V为例1求y二sinx（0＜x＜。）与x轴所围图形绕y轴旋转所得立体的体积。解选X为积分变量，XE［o，d。在k，d上取小区间》，X十dX〕，…     

关于旋转体体积的一种算法

在直角坐标系中由平面图形绕其平面内的坐标轮（x轴或y轴）旋转所得的四种旋转体的体积与围成平面图形的边界有关，本文讨论四种体积公式及参数方程表示边界组成时的体积公式。分别绕x轴、y轴旋转而成的旋转体的体积如何计算？1．平面图形绕x轴旋转而成旋转体的体积V；z，同济大学《高等数学》上册P．346给出公式对①应用分部积分法上式②中令地。，显然地。（如图2）是半正分别为f（b），f（a）高分别为b，a的圆柱体体议之差。八I7＿＿＊＿【、，J／，W＼尸／，＼／，门＼Lc，y，——／汀DrJ＼工IJ【工10JUJ7w2I——乙”‘“J＼一／…     

极坐标系下旋转体体积元素的直接构造法

用元素法的思想,讨论了在极坐标系下平面图形绕极轴旋转一周所得旋转体体积元素的直接构造法,进行了这种构造正确性的理论证明,给出算例.     

旋转体体积计算中的微元法思想应用

通过讨论几类不同数学模型下旋转体体积的计算方法,阐述了"微元法"思想在其中的重要应用价值.特别地,还考虑到两类旋转轴穿过旋转区域内部的情况,并给出了相应的体积计算方法.此外,在利用定积分和二重积分计算外,基于"微元法"给出了一类旋转体体积的曲线积分计算方法,并说明了其一般性.     

极坐标系下曲边扇形的旋转体体积公式

利用定积分的有关知识,对极坐标系下曲边扇形绕极轴旋转所得旋转体体积公式进行了推广,并推导证明了曲边扇形绕平面中任意直线旋转所得旋转体的体积公式,并借助实例进行了说明.     

旋转体体积计算的一般公式

旋转体体积计算的一般公式程曹宗（北京工业大学计算机学院１０００４４）关于旋转体体积的计算，这是一个熟知的问题，在高等数学教科书中均有这方面内容介绍，其结论是：若一连续曲线ｙ＝ｆ（ｘ）的弧ＡＢ与直线ｘ＝ａ，ｘ＝ｂ及ｘ轴所围成的平面图形绕ｘ轴旋转一周，产...     

例析多面体、旋转体的外接球问题

<正>有关球的组合体问题是高中数学的重要内容之一,也是高考考查的重点.尤其是多面体、旋转体的外接球问题,更是同学们学习的难点.下面通过高考题举例分析这类问题的解答方法,供大家参考.1旋转体的外接球在研究旋转体外接球相关问题时,关键是找到两个旋转体公共旋转轴的轴截面,将立体问题转化成平面问题来解答.     

A multisheet plane figure and its medial axis

A multisheet plane figure is a projection onto the Euclidean plane of a surface whose every point has a neighborhood biuniquely projectable onto the plane. The notion of a multisheet plane figure is a generalization of the usual notion of a plane figure for the case when the boundary contains self-intersecting curves and pairwise intersecting ones. The medial axis of a usual plane figure is the set of points equidistant from the boundary. In this paper we introduce the notion of the medial axis of a multisheet plane figure and study its properties. Medial axes have numerous applications in engineering and computer science.     

从Beltrami-Schaefer应力函数导出几个特殊问题的应力函数

本文从弹性力学中的Beltrami-Schaefer应力函数出发,导出了扭转问题、平面问题、轴对称问题和回转体扭转问题的应力函数.     

The Washer Method

<正>You've learned the disk method to use integral finding the volume of solid revolution.You'll learn how to use other method for finding the volume of a special type of solids of revolution.Solids of revolution are used commonly in industry.Sometimes,slicing a solid of revolution results in disks with holes in the middle.It's called washer method.The washer is formed by revolving a rectangle about an axis,as shown in Figure 1&2.     

Low Frequency Scattering by Spheroids and Disks 1. Dirichlet Problem for a Prolate Spheroid

The problem of scattering of a scalar plane wave by a prolatespheroid of revolution is solved for Dirichlet boundary condition,arbitrary major to minor axis ratio, and arbitrary incidentdirection. The solution is obtained by using an iterative methodapplied to solutions of the corresponding potential problemand is expressed as a series of products of Legendre and trigonometricfunctions, and ascending powers of wave number. A recursionrelation for the coefficients in this series is derived.     

Stressed state of a circular hollow porous liquid-saturated cylinder rotating around its axis with constant angular velocity

We have obtained an exact solution of the plane problem for a porous tube rotating around its fixed axis of symmetry. The material of the tube is saturated with an ideal compressible liquid. Within the framework of the Bowen theory, for constructing the initial relations, we take into account the interconnections between stress tensors, strain tensors, relative density of the liquid filler, and varying porosity of the material. We present relations for the radial displacements, components of the stress tensor and densities in the skeleton and liquid filler, and also the porosity and mass concentration of the mixture. We have carried out a numerical analysis of the radial distributions of these characteristics for solid and hollow cylinders made of sandstone and saturated with kerosene. The critical numbers of revolution for tubes of saturated and dry materials have been found.     

First integrals of the equations of motion of a symmetric gyrostat on a perfectly rough plane

The problem of the motion of a dynamically symmetric gyrostat without slipping on a fixed horizontal plane is investigated. When the surface of the gyrostat and the distribution of the masses in it satisfy a certain condition, supplementing and developing the results obtained by Mushtari [Mushtari KhM. The rolling of a heavy solid of revolution on a fixed horizontal plane. Mat Sbornik 1932; 39(1, 2):105–26], an explicit form of two first integrals of the equations of motion of the gyrostat, in addition to the energy integral, is presented.     

Twisted Surfaces with Null Rotation Axis in Minkowski 3-Space

We examine curvature properties of twisted surfaces with null rotation axis in Minkowski 3-space. That is, we study surfaces that arise when a planar curve is subject to two synchronized rotations, possibly at different speeds, one in its supporting plane and one of this supporting plane about an axis in the plane. Moreover, at least one of the two rotation axes is a null axis. As is clear from its construction, a twisted surface generalizes the concept of a surface of revolution. We classify flat, constant Gaussian curvature, minimal and constant mean curvature twisted surfaces with a null rotation axis. Aside from pseudospheres, pseudohyperbolic spaces and cones, we encounter B-scrolls in these classifications. The appearance of B-scrolls in these classifications is of course the result of the rotation about a null axis. As for the cones in the classification of flat twisted surfaces, introducing proper coordinates, we prove that they are determined by so-called Clelia curves. With a Clelia curve we mean a curve that has linear dependent spherical coordinates.     

The steady motions of a heavy ellipsoid filled with liquid on a plane with friction

The motion of a heavy uniform thin-walled ellipsoid of revolution, completely filled with an ideal incompressible liquid, performing uniform vortex motion is investigated. It is assumed that the ellipsoid is situated on a horizontal plane, from the side of which a normal reaction and a force of viscous sliding friction act on it. The equations of motion of the system, suitable both in the general case and in limiting cases of zero ellipsoid mass or zero liquid mass, are set up. Steady and periodic motions of the ellipsoid with the liquid are obtained. The conditions for uniform rotations of the ellipsoid about a vertically situated axis of symmetry to be stable are obtained.     

动力点圆力偶作用于弹性全空间的解及其性质*

本文给出动力点圆力偶作用于弹性全空间原点的解,并讨论它的性质.将脉冲荷载沿以原点为心、α半径,在z=0平面上的圆周切向均匀分布,当a→0时经积分运算即得问题的解.当此动力点圆力偶的强度按sinωt变化时,在弹性全空间中以z轴为轴,原点为顶点的锥面在任何时刻均为零应力面.以这些锥面为边界的回转体受按sinωt而变化的扭矩作用的动力扭转问题的解可由本文的解得出.