几个实驗

一、运动体速度与桥面压强之間关系的演示演示可用下述自制仪器进行。框架ABCD[图1(b)]的組成部分是长70厘米阔15厘米的木板AB和CD及高20厘米的支架AC和BD。位于上面的AB板中間凿孔,使桥拱能在孔內自由升降庞蒀_1K和D_1M同长杆OT固定。OT的左端用鉸鏈釘在支架AC上,使能在垂直平面內繞O点轉动。OT的     

美国部分高等学校研究生考题分析和介绍(三)

(四)刚体平面平行运动方面的题目和分析力学(用拉格朗日方程解题)方面的题目,总是占相当的比例。这些是经典力学中的传统内容。刚体平面平行运动是日常生活和生产中 最常见的一种运动,它涉及刚体动力学的一些基本物理量的计算和所有基本定理的运用。与刚体定点运动相比,刚体平面平行运动方面有更多的题目可出。分析力学代表经典力学的进一步发展,它是理论物理的基础,它的重要性是很清楚的。 [题5]两根相同的均匀杆AB和BC,每根杆的质量为m,长为2a,在 B点处为光滑连接。 C点能沿一光滑水平轨道运动。 AB能在竖直平面内绕固定点A自由转动。…     

点内电子-电子库仑作用会引起退相干么?

利用一个开放的多端Aharonov—Bohm(AB)装置研究了存在点内库仑作用时，电子通过量子点时的相干性．作者发现点内库仑作用不会引起任何退相干效应，即电子隧穿通过量子点是完全相干的．另外，作者还发现，在两端AB装置中，电导AB振荡的振幅非对称性来源于受限的结构和库仑作用两方面．因此，不能把振幅的非对称性和退相干过程联系起来．     

牛顿第二定律演示实验 牛顿第二定律演示实验的改进

在进行牛顿第二定律的教学时,我们做了一个简单直观的演示,收到较好的效果,现介绍于下。实验器材包括铁架台(附夹子与铁棍)两个;有槽木板两个(长约1.2米);钢球三个,其中两个的质量相等,设为m,另一个质量为2m。实验装置如图1所示.使AB=2A_1B_1,AC=A_1C,E为A_1C的中点。C处放一长方木块,好让小球与它撞击而发声。     

共点力平衡问题中几类特殊题型分析

主要对高中共点力平衡问题的几种常见的特殊题型进行了归类分析. 归纳了共点力平衡问题中的动态 平衡类问题、 杆类问题、 滑轮类问题以及连接体类问题的特点及其解题策略     

物体平衡问题的解题方略

物体平衡是一种重要的物理模型，其实质是力的平衡．研究对象的选取与变换、力的等效处理、平衡力之间的制约关系是我们在解决物体平衡问题时进行解题决策的三个基本着眼点．     

平衡点对应的最大速度在各类物理题中的应用

平衡点对应最大速度是许多题中特点鲜明的一种隐含条件，利用平衡点处合力为零，列出平衡方程即可解题；或根据具体情况抓住其规律，便可事半功倍，轻松解题．     

改进DIS装置测量物体转动时所受杆支持力的方向

利用大学物理知识及原理,改进DIS-向心力研究装置,测量在非惯性转动参照系下物体运动所受杆支持力的方向,从而精确判断物体在转动过程中所处状态,如加速（或减速）或匀速等。     

超声变幅杆的超声精密加工

本文探讨了超声变幅杆的精密加工．作者研制了双刀反间进给超声车削装置和单刀正向进给超声车削装置，采用了具有频率跟踪系统的晶体营型超声波发生器．超声车削设备连续140min工作时，频率漂移量只有29HZ，最高温度只有38℃．试验结果表明，加工精度可达IT7－ITS，表面粗糙度几可达0．4－0．8m，加工效率提高15倍，有效地解决了超声变幅杆的精密加工难题．     

力矩演示器的制作与使用

在力矩的教学中，制作力矩演示器，演示转动物体受力平衡时不只决定于力而且还决定于力臂，并能清楚认识有固定转轴物体的平衡条件．1结构装置如图所示，在一水平支持台上有一沿水平轴可以转动的圆木轮，轮缘有槽沟，使线不致脱出，轮上固定有二长杆相交成30”的角，在两杆对应     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

On the calculation of the bremsstrahlung in the region of the plasma frequency

On the basis of the classical theory of radiation produced in incomplete Coulomb interaction, a formula is derived for the coefficient of the bremsstrahlung of fully ionized plasma. In the region of rectilinear approximation a comparison is made with the results of the quantum formula derived from the Born approximation. Furthermore, the influence of dispersion upon the emission coefficient is taken into account; some relations for the region of dispersion are given.     

Dependence of the Intensity of the Spectral Lines and the Composition of the Sample and the Plasma Parameters of the Unipolar Arc

The investigation was made of the dependence of the intensity of Tl, Ga, Mo, Mg, Mn, Sn, Bi, Ni, Zn, Pt and Au spectral lines and the plasma parameters (temperature T, electron concentration n_e, degree of 6 ionnization α) from concentration of lithium additive.     

Extracting the wavefunction of the LSP at the LHC

We consider associated production of squarks and gluinos with the lightest supersymmetric particle (LSP), or states nearly degenerate in mass with it. Though sub-dominant to pair production of color SU(3)-charged superpartners, these processes are directly sensitive to the wavefunction composition of the lightest neutralinos. Exploiting event-shape variables - including some introduced here for the first time - we are able to identify the composition of the LSP by selecting events involving a single high-pT jet recoiling against missing transverse energy. We illustrate the proposed technique on a set of benchmark cases and propose methods for applying these results in more realistic experimental environments.     

Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

On the Question of the Source of the Apokamp

Technical Physics - The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage...