物体相关速度的分析方法

在中学物理教学中,经常遇到这样一类问题:几个物体的运动存在着某种关系,根据其中一个物体的运动速度求其它物体的运动速度,这类问题称为相关速度问题.相关速度问题一般用微元法、速度分解法、功能分析法等方法来求解.     

求圆周运动物体的临界速度

“临界速度”就是指物体运动“刚好出现”或“刚好不出现”某种现象时的速度.求临界速度是处理临界问题的关键,其基本思惟方法是假设推理法.本文将圆周运动物体的几种临界速度的求解作一归纳. 一、线端小球在竖直面内做圆周运动时,刚     

例谈物体运动速度取到最值的一条普遍规律

在物理教学中,常会有这样一类问题,某运动物体,其受力方向与运动方向的夹角在时刻变化.求运动过程中,该物体速度的最值大小和方向.对于这样一类问题的处理,学生普遍反映困难较大.其实要是掌握了这类问题内     

如何求物体做曲线运动的时间

曲线运动是一种常见的复杂运动,对曲线运动的问题,学生往往感到无从下手.本文如何求解物体做曲线运动的时间例谈一二. 一、利用研究曲线运动的基本方法求时间 研究曲线运动的基本方法--运动的合成与分解,即先将一个复杂的曲线运动,看成物体同时参与几个简单的分运动,研究各个分运动,然后再将描述这些分运动的物理量进行合成,就可以得出复杂曲线运动的规律.这中间有一个很重要的性质即分运动与合运动具有等时性,利用这一性质可以求物体做曲线运动的时间,这种方法是最基本的,适用范围较广.     

浅析平抛运动中物体速率的变化率

在高三复习题中有这样一道选择题,题目如下:题目　做平抛运动的物体(　　)A .每秒内速率的变化相等B .每秒内速度的变化相等C .水平飞行的距离只与初速度的大小有关D .水平飞行的距离只与抛出点的高度有此题的正确答案是选项B ,但选项A为什么是错误的?有一些学生搞不清楚.这里涉及平抛运动的物体速率的变化率,下面笔者就对这一问题谈谈自己的一些粗浅看法.我们可用两种不同的方法来分析.一、图解法设做平抛运动的物体初速度为v0 ,1s后图1的速度为v1,2s后的速度为v2 ,3s后的速度为v3 .由于做平抛运动的物体在水平方向上的分运动是匀速直线…     

两个物体一起匀加速运动的规律及其应用

我在研究两个物体一起运动的过程中,通过这一类题目的解题过程,发现了一点规律,今通过下列题目来说明.题如图1所示.用恒力F拉着物体沿光滑的水平面运动,物体的质量分别为m1、m2,求轻绳的张力大小.     

巧用功能关系求物体的加速度

我们常用牛顿第二定律求物体的加速度,但若能根据功能关系求出速度的表达式,则应用待定系数法就可求出物体的加速度．下面举例说明这一方法在解题中的运用．     

4 研究平抛物体的运动

[实验目的]1.用实验方法描出平抛物体的运动轨迹;2.从实验轨迹求平抛物体的初速度.[实验原理]平抛物体的运动可以看作是两个分运动的合运动:一是水平方向的匀速直线运动,另一个是竖直方向的自由落体运动.令小球做平抛运动,利用描迹法描出小球的运动轨迹,即小球作平抛运动的曲线,建立坐标系,测出曲线上的某一点的坐标x和y,根据重力加速度g的数值,利用公式y=1/2gt~2求出小球的飞行时间t,再利用公式x=vt,求出小球的水平分速度,即为小球作平抛运动的初速度.     

4 研究平抛物体的运动

[实验目的]1.用实验方法描出平抛物体的运动轨迹;2.从实验轨迹求平抛物体的初速度.[实验原理]平抛物体的运动可以看作是两个分运动的合运动:一是水平方向的匀速直线运动,另一个是竖直方向的自由落体运动.令小球做平抛运动,利用描迹法描出小球的运动轨迹,即小球作平抛运动的曲线,建立坐标系,测出曲线上的某一点的坐标x和y,根据重力加速度g的数值,利用公式y=(1/2)gt~2求出小球的飞行时间t,再利用公式x=vt,求出小球的水平速度,即为小球作平抛运动的初速度.     

中学物理中物体平衡问题例析

每年高考都很重视物体平衡问题,笔者在平时的教学过程中发现学生对于共点力作用下物体的平衡问题总觉得很难,主要是没有认真总结,找出规律.下面我们结合例题予以总结,以不变应万变,突破此类问题.平衡状态分两种情况:一种是静态平衡,物体运动的速度v=0,物体的加速度a=0;另一种是动态平衡,物体运动的速度v≠0,物体的加速度a=0.一、静平衡问题的分析     

浅析理想模型状态下空气阻力的计算

对大型物体和快速运动的物体,空气对它们的阻力是不可忽略的,其计算也是很复杂的。本文利用理想化的空气分子模型推导了低速运动和高速运动物体所受的空气阻力计算公式,使空气阻力的计算简单化,便于计算。     

关于透镜成像的讨论

高中物理课本讨论了透镜成像的基本规律,本文进一步探讨了透镜成像的其他规律,如物像间的距离,物像移动的方向及物像移动的速度     

一种基于改进帧差法的运动目标检测

针对视频中的运动目标离摄像头较近时由于形状的变化而导致目标边界测定不准确的问题,在帧间差分法的基础上,提出了一个求精运动目标边界的算法。先用得到边界值计算目标中心点,再对视频中的运动目标进行运动距离和速度的检测,并在Matlab中进行仿真。实验结果表明,该算法对帧差法的结果进行求精后,得到的运动目标的状态值更接近于实际情况,改进的算法更适合于视频中运动目标形状变化较大的情况下进行运动目标状态的检测。     

基于单片机的搬运机器人设计

以STM32单片机作为主控芯片,设计了由履带式移动平台和六自由度机械臂组成的搬运机器人,应用无线通信技术、嵌入式技术和PWM波脉宽调制技术,对机器人进行无线操控以及使其实现搬运功能。经测试,该搬运机器人能够完成对物体的精准定位和抓取,而且工作稳定、可控角度大、移动速度快、灵活性高,具有一定的应用价值。     

Acquisition of behavioral control by the auditory features of an imprinting object

Presentations of a visible moving object immediately suppressed ongoing distress vocalization in newly hatched ducklings, but presentations of only the auditory features of the object initially had no effect. However, as the ducklings received more and more exposure to the visible moving object, the object’s auditory features gradually acquired the ability to suppress distress calls themselves. These auditory features failed to develop suppressive properties in ducklings which received prolonged exposure to those features but never saw the object in motion. The gradual acquisition of behavioral control by the auditory features of a moving object is taken to represent the essence of the imprinting process.     

一种有效的基于运动矢量场的压缩域运动对象分割算法

In this paper an efficient compressed domain moving object segmentation algorithm is proposed, in which the motion vector (MV) field parsed from the compressed video is the only cue used for moving object segmentation. First the MV field is temporally and spatially normalized, and then accumulated by an iterative backward projection to enhance salient motions and alleviate noisy MVs. The accumulated MV field is then segmented into motion-homogenous regions using a modified statistical region growing approach. Finally, moving object regions are extracted in turn based on minimization of the joint prediction error using the estimated motion models of two region sets containing the candidate object region and other remaining regions, respectively. Experimental results on several H.264 compressed video sequences demonstrate good segmentation performance.     

The effect of context on students’ reasoning about forces

When attempting to solve closely related problems in science, students will often respond to irrelevant contextual features in the questions rather than generalizing their conceptions over the range of relevant situations. In this study, a group of 40 students (one group of 15‐16‐year‐olds and another of preservice science teachers) was surveyed and interviewed to determine the effect of context on the reasoning which they used to solve problems concerning the forces acting on objects in linear motion. It was found that the younger group of students were influenced by contextual features such as the speed, weight and position of the moving object, the direction of the motion and their own personal experience of the context. There were clearly two types of contextual effects ‐‐ primary and secondary, which are described. The older group of students was generally less affected by context and thus more consistent in their reasoning.     

基于视频的运动目标检测跟踪模型的应用研究

本文采用了一种运动目标存在情况下的背景重建算法,能较好地抑制外界环境变化带来的影响。该运动目标检测算法通过一定数量帧的学习、统计,找到各坐标点像素灰度等级的分割阈值。在对当前帧图像进行背景差分后,分割出运动目标区域。若存在运动目标,则根据串行边界跟踪算法获得运动目标轮廓。获得边界后,模型将绘制方框显示运动物体,并发出警报。该运动目标检测模型用VisualC＋＋给予实现。     

Extracting Moving Objects Based on Morphological Motion Filter

This paper presents a new approach to the extraction of a moving object from video sequence.The method is based on morphological motion filter using connected operator and a propsed new filtering criterion.The morphological motion filter aims to detect motion which is distinct from that of the background,and thereby locates independently moving physical objects in the secnes.Experiments show that the algorithm can extract object from moving backgrounds efficiently.     

EDUCATION AND THE AGED: SOCIAL AND CONCEPTUAL CHANGES IN JAPAN

Japan is moving into an aging society at a greater speed than any other country in the world has ever experienced. As this speed is very rapid, the concept of life in the aged life‐cycle stage which has emerged has not been fully established yet; here the cultural lag phenomenon is acutely observed. Among many possible activities, however, learning activities will be expected to have increasing popularity among aged persons as a source of happiness and inspiration for the fulfillment of their lives. Since not only young persons, but also aged persons, are involved in learning activities, the concept expressed by the term education is changing into a broader one to include the transmitting of values, knowledge, and skills through secondary communication.