共查询到20条相似文献,搜索用时 109 毫秒
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对变质量问题的实验研究王晓耕,郝利(承德石油高等专科学校,067000)在大学物理教学和习题中常遇到变质量问题,我们在气垫导轨的滑块上增加了载沙槽装置,在导轨上端悬挂一沙漏斗,当载沙槽、滑块组成的系统在外力作用下沿导轨运动时,漏斗中的沙子匀速地落在运... 相似文献
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在普物实验中,气轨上通常研究的是恒力作用下的匀加速运动,学生对变力情况下的力学规律的研究一般仅限于理论探讨的范畴。笔者通过在气垫导轨上增加一个支板作为附件,利用它达到改变作用于滑块上力的方向的目的,使对恒力作用下的匀加速系统力学规律的研究转化为变力作用下的变加速系统力学规律的研究. 相似文献
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做功的一般表达式为W=Fscosθ,F是恒力.如果力是变力,就不能套用这个公式.笔者根据自己的教学实践,针对不同的题设条件,总结出以下几种求变力做功的方法.1 用平均力代替变力求变力的功 当变力与质点位移大小成线性关系时,平均力F=(F1+F2)/2,变力对质点所做的功,在数值上等于平均力做的功. 相似文献
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从Мещерский方程出发,建立变质量力学系统的高阶D'Alembert-Lagrange原理,导出变质量完整力学系统的各类高阶运动微分方程.结果表明,它们扩充和优化了完整力学的相关理论.
关键词:
变质量完整力学系统
高阶力变率
高阶D'Alembert-Lagrange原理
高阶运动微分方程 相似文献
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本文陈述了如何在气垫导轨上借助于柔软的金属细链来验证变力情况下的动能定理、动量定理及物体的运动方程等力学规律.并详细地叙述了实验原理,介绍了实验装置及实验方法,分析概括了产生实验误差的原因. 在普通物理学实验中,对变力问题的研究一直是一个非常棘手的问题.我们曾借助于柔软的金属细链与气垫导轨结合起来,来研究变力问题,很好地验证了变力情况下的力学规律. 相似文献
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利用"微元"思想借助Excel软件的计算功能推演出在变力作用下的运动规律,并可以描绘出各物理量之间的关系图像.列举了三个实例,简谐运动、洛伦兹力作用下的圆周运动、带电小球在复合场中的运动. 相似文献
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在解决物理习题中,经常涉及两类变力:带电粒子垂直于匀强磁场方向运动时受到的洛伦兹力和闭合电路的部分导体在垂直切割磁感线时受到的安培力.这两种变力除了都是磁场力这一性质上的联系外,还具有一个重要的共同点,即力的大小都与速率成正比. 相似文献
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Mei symmetry and Mei conserved quantity of Appell equations for a variable mass holonomic system 下载免费PDF全文
Mei symmetry and Mei conserved quantity of Appell
equations for a variable mass holonomic system are investigated.
Appell equations and differential equations of motion for a variable
mass holonomic system are established. A new expression of the total
first derivative of the function with respect of time t along the
systematic motional track curve, and the definition and the
criterion of Mei symmetry for Appell equations under the
infinitesimal transformations of groups are given. The expressions
of the structural equation and Mei conserved quantity for Mei
symmetry in Appell are obtained. An example is given to illustrate
the application of the results. 相似文献
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Noether‘s theory of a rotational relativistic variable mass system is studied.Firstly,Jourdain‘s principle of the rotational relativistic variable mass system is given.Secondly,on the basis of the invariance of the Jourdain‘s principle under the infinitesimal transformations of groups,Noether‘s theorem and its inverse theorem of the rotational relativistic variable mass system are presented.Finally,an example is given to illustrate the application of the result. 相似文献
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Effects of variable properties on MHD heat and mass transfer flow near a stagnation point towards a stretching sheet in a porous medium with thermal radiation 下载免费PDF全文
The effect of variable viscosity and thermal conductivity on steady magnetohydrodynamic(MHD) heat and mass transfer flow of viscous and incompressible fluid near a stagnation point towards a permeable stretching sheet embedded in a porous medium are presented,taking into account thermal radiation and internal heat genberation/absorbtion.The stretching velocity and the ambient fluid velocity are assumed to vary linearly with the distance from the stagnation point.The Rosseland approximation is used to describe the radiative heat flux in the energy equation.The governing fundamental equations are first transformed into a system of ordinary differential equations using a scaling group of transformations and are solved numerically by using the fourth-order Rung-Kutta method with the shooting technique.A comparison with previously published work has been carried out and the results are found to be in good agreement.The results are analyzed for the effect of different physical parameters,such as the variable viscosity and thermal conductivity,the ratio of free stream velocity to stretching velocity,the magnetic field,the porosity,the radiation and suction/injection on the flow,and the heat and mass transfer characteristics.The results indicate that the inclusion of variable viscosity and thermal conductivity into the fluids of light and medium molecular weight is able to change the boundary-layer behavior for all values of the velocity ratio parameter λ except for λ = 1.In addition,the imposition of fluid suction increases both the rate of heat and mass transfer,whereas fluid injection shows the opposite effect. 相似文献
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Mei symmetry and Mei conserved quantity of Appell equations for a variable mass holonomic system of relative motion 下载免费PDF全文
Mei symmetry and Mei conserved quantity of Appell equations for a variable mass holonomic system of relative motion are studied.The definition and criterion of the Mei symmetry of Appell equations for a variable mass holonomic system of relative motion under the infinitesimal transformations of groups are given.The structural equation of Mei symmetry of Appell equations and the expression of Mei conserved quantity deduced directly from Mei symmetry for a variable mass holonomic system of relative motion are gained.Finally,an example is given to illustrate the application of the results. 相似文献
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Lie symmetry and the generalized Hojman conserved quantity of Nielsen equations for a variable mass holonomic system of relative motion 下载免费PDF全文
Lie symmetry and the generalized Hojman conserved quantity of Nielsen equations for a variable mass holonomic system of relative motion are studied. The determining equation of Lie symmetry of Nielsen equations for a variable mass holonomic system of relative motion under the infinitesimal transformations of groups is given. The expression of generalized Hojman conserved quantity deduced directly from Lie symmetry for a variable mass holonomic system of relative motion is obtained. An example is given to illustrate the application of the results. 相似文献
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Based on the total time
derivative along the trajectory of the system
the definition and the criterion for a unified symmetry of nonholonomic
mechanical system with variable mass are presented in this paper. A new
conserved quantity, as
well as the Noether conserved quantity and the Hojman conserved quantity,
deduced from the unified symmetry, are also obtained. An example is given to
illustrate the application of the results. 相似文献