牛顿第二定律演示器

用一细长的电镀杆(或用细玻璃管嵌在木条上)作直轨道1,悬挂式小车2正面有一开口,可以取放砝码,下端安一支笔(可用一细笔管安上香烟的过滤嘴或泡沫塑料蘸墨水即可),以便自动记录小车的位置。直轨道的右上方有一个略小于直轨一半长度并可绕一端转动的斜槽轨道3,在后板适当位置做一弧形狭缝,用螺丝可将斜槽固定在所需     

对牛顿第二定律实验的改进

对牛顿第二定律实验的改进吴培科（江苏新沂市教研室２２１４００）现行教科书中都是选用物理小车研究物体加速度与力、与质量间的关系，实验结果很不准确，一般误差可达１０％，甚至更多．实验需要通过作出ａ一无图象得出结论，－““””“——””－Ｍ—～””———”...     

牛顿第二定律验证实验的改进

牛顿第二定律是动力学的核心,其验证是普通物理实验的基础实验之一,通常是采用气垫导轨配合数字毫秒计时器来验证的.     

牛顿第二定律实验的改进

通过改进牛顿第二定律的装置，解决了拉力直接测量的问题，减少了学生的知识障碍。     

在气轨上验证牛顿第二定律实验的剖析

气垫导轨是60年代初出现在物理实验室的低摩擦实验装置,它为改善普物力学实验提供了很好的条件。但是要使实验达到比较高的水平,还必须考虑一些问题。本文仅就气轨上验证牛顿第二定律的实验进行分析,主要讨论实验应获得的结果、困难和措施,此外也讨论了对学生的要求。     

牛顿第二定律在引力场中失效

牛顿第二定律只阐明物体的加速度ａ、质量ｍ和所受合外力Ｆ三者间的关系 .对于质量相同的物体 ,加速度跟受到的合外力成正比 ;相同的合外力作用于质量不等的物体 ,其加速度跟质量成反比 .在国际单位制中 ,该定律的数学表达式为 :Ｆ =ｍａ…………………… (1 )此定律适用于惯性参照系 ,式中的ｍ叫物体的惯性质量 .至于物体所受的力跟它的质量是否有关 ?却未涉及 .理论和实践都证明 ,物体除了受孤立的万有引力或重力之外的不平衡外力作用时 ,牛顿第二定律都适用(在经典力学范围内 ) ,并且这种合外力跟物体的质量无关 .然而在孤立的引力场或重…     

公式F=ma中的力从哪来?

力的概念早在Hamihonian力学的框架内就失去了存在的合理性，但它却一直贯穿于我们处理力学问题的思维并在教科书中快乐地存在着．本文(发表在Physics Today，Oct．2004．)中，2004年度诺贝尔物理学奖得主、MIT物理学教授Frank Wilczek从科学发展史、科学方法论以及文化与心理学的角度研究了这一悖论，读来令人有茅塞顿开之感．我们迅速翻译了这篇好文章，以飨国内的广大物理学爱好者。     

公式F=ma中的力从哪来?(之三)

（上接2005年第11期第786页） 3 文化差异 如我们所见,力的概念定义了一种文化.在先前发表的此系列的专栏文章（Physics Today,2004年10月,第11页以及2004年12月,第10页）中1）,我说明了通过对力这一概念的诠释（实际上是关于力的附加假设）,公式F=ma是如何被赋予意义的.这样的诠释有点民间传说的味道.它既包含了在适当条件下我们可以从近代〈物理〉2）基础得到的近似,也包含了从经验中抽象出的略嫌粗放的推广（例如关于摩擦力和弹性行为的所谓的“定律”）.     

Newton's First Law Revisited

The formulations of Newton's first law in Newton's Principia and in modern textbooks are examined critically. A special effort is made to differentiate clearly between definitions and nontrivial facts of nature, and this is done in as primitive terms as possible, with emphasis on the projective structure. A somewhat novel characterization of the term free particle is proprosed, and a new, coordinate-independent definition of the term straight line is provided. The analysis is performed in 4-dimensional spacetime, and separately for the idealized case of the absence of gravity and for the dynamics in the presence of gravity.     

Configurational Entropy and Newton's Law in Double Sine‐Gordon Braneworlds

The Shannon‐like entropic measure of spatially localized functions for a 5D braneworld generated by a double sine‐Gordon (DSG) potential is evaluated. The differential configurational entropy (DCE) has been shown in several recent works to be a configurational informational measure (CIM) that selects critical points and brings out phase transitions in confined energy models with arbitrary parameters. The DSG scenario is selected because it presents an energy‐degenerate spatially localized profile where the solutions to the scalar field demonstrate critical behavior that is only a result of geometrical effects. As is shown, the DCE evaluation provides a method for predicting the existence of a transition between the phases of the domain wall solutions. Moreover, the entropic measure reveals information about the model that is capable of describing the phase sector where resonance modes on the massive spectra of the graviton is obtained. The graviton resonance lifetimes are related to the existence of scales on which 4D gravity is recovered. Thus, the critical points defined by the CIMs with the existence of resonances and their lifetimes are correlated. To extend the research regarding this system, the corrections to Newton's law coming from the graviton modes are calculated.     

论开普勒第二定律的发现方法

1引力的物理思想 一些物理学史书籍讲到开普勒在发现天体运行三定律后，开始探索是什么原因使天体这样运动，但没有成功．这听起来很合理，但不符合历史事实．     

Microscopic aspects implied by the Second Law

It is conventional to try to arrive at the Boltzmann principle and the Second Law starting with the laws of dynamics at the microscopic level. In this article the opposite view is presented: Starting with the Second Law, microscopic properties are derived. A classical result of Wien is developed into a general theorem, and the possibility of deriving the Boltzmann principle as a consequence of Carnot's theorem is discussed.     

A Reversible Theory of Entanglement and its Relation to the Second Law

We consider the manipulation of multipartite entangled states in the limit of many copies under quantum operations that asymptotically cannot generate entanglement. In stark contrast to the manipulation of entanglement under local operations and classical communication, the entanglement shared by two or more parties can be reversibly interconverted in this setting. The unique entanglement measure is identified as the regularized relative entropy of entanglement, which is shown to be equal to a regularized and smoothed version of the logarithmic robustness of entanglement. Here we give a rigorous proof of this result, which is fundamentally based on a certain recent extension of quantum Stein’s Lemma, giving the best measurement strategy for discriminating several copies of an entangled state from an arbitrary sequence of non-entangled states, with an optimal distinguishability rate equal to the regularized relative entropy of entanglement. We moreover analyse the connection of our approach to axiomatic formulations of the second law of thermodynamics.     

Edward Gerjuoy: From Physics to Law and Back Again

Theoretical physicist Edward Gerjuoy discusses his family background, elementary and secondary education in Brooklyn, New York, undergraduate studies at City College, graduate work at the University of California at Berkeley, research during World War II, and subsequent career at the University of Southern California, New York University, the General Atomics Laboratory, the Radio Corporation of America, and the University of Pittsburgh, as well as his work as a lawyer and service as a judge on the Pennsylvania Environmental Hearing Board in Pittsburgh.     

从功能定理到热力学第一定律到普遍的能量守恒定律

着重阐明功和能的根本意义，在质点的功能定理和质心系的基础上说明摩擦生热及热力学第一定律的意义，最后说明普遍的能量守恒定律的建立过程及其意义。