Based on the Poisson bracket and the discriminant of integral of motion, we prove the problem that the moment of momentum is the integral of motion when the mass point is affected by central force.
运用泊松括号，依据运动积分判别式，证明了质点受有心力作用时，其动量矩是运动积分的问题。
As mass production techniques were refined in the 19th century, the price of pianos dropped to the point that a larger proportion of the population could afford to own them.
随着19世纪大规模生产技术的改进，钢琴的价格下降到更多人都买得起的程度。
Excessively skinny models have been a point of controversy for decades, and two researchers say a model's body mass should be a workplace health and safety issue.
几十年来，过瘦的模特一直是争议的焦点，两名研究人员表示，模特的体重应该是职场的健康和安全问题。
The cinema did not emerge as a form of mass consumption until its technology evolved from the initial "peepshow" format to the point where images were projected on a screen in a darkened theater.
电影播放技术由最初的“西洋镜”的形式演变而来，直到其发展到一个时期；在这个时期中，影像被投影到幽暗的影院屏幕之上，电影才作为一种大众消费的形式而出现。
The cable would connect with some point on Earth located at the equator, and would allow mass to be transferred to orbit using electricity instead of rocket fuel.
该电缆将连接一些位于地球赤道上的点，这将允许群众被运送到到轨道使用电来代替火箭燃料。
Like all clouds, it forms when the air reaches its dew point, which is the temperature to which an air mass must be cooled for the water vapor in it to condense into liquid droplets.
和其他云一样，它是当空气达到凝结点，即空气团的温度冷却到使其中的水蒸气凝结成液态水滴的温度时形成的。
Astronomers believe that only 50% of the mass of the dilapidated star gets swallowed by the black hole; the other half gets "burped" back out into space before it reaches the point of no return.
天文学家们认为被黑洞吸入的恒星只有50%的质量会被它吞掉；而剩下的一半会因黑洞“打嗝”而在万劫不复之前返回外界。
This marks precisely—to within a few thousand years—the point of mass extinction on the land.
这明确标志着正是在这几千年中，发生了陆地上的大规模灭绝。
The point: that a period of a pendulum is independent of the mass - the steel ball, plus one professor - hanging from it.
目的是证明：钟摆周期和质量无关—那个铁球的，以及挂在上面的那个物理教授的。
But the basic idea is, then, that the center of mass will always in stable configuration line itself up below the point of suspension.
但是基本概念是，物体的重心将一直，处于稳定的结构线上，在悬挂点下面。
But the center of mass — - you see it when I balance it on my finger — is way below the suspension point.
而重心-，你们可以看到-，在悬挂点下方。
Several of the pager messages point to the mass of confusion and rumour-mongering that set in after the first plane hit the north tower.
有几条寻呼机信息表明在第一架飞机撞上北塔之后，人们产生了大量的困惑，谣言四起。
So efficiency tends to decrease with increasing size once firms have passed the point where they can take full advantage of mass production.
所以当一个企业越过了它能获得的规模效应的最高点后，它的规模和效率则呈反比。
In factories that are designed on the principles of mass production, stopping an assembly line to correct a problem at any one point stops work at all points.
在依据批量生产设计的工厂里, 一旦因纠正一个错误而停止组装线就意味着停止全部的工作.
The complexity is rapidly reaching a point of critical mass, where one single developer can no longer know everything needed to be proficient at his or her job.
复杂性迅速地到达一个临界点，即一个单独的开发者已经不能精通他或她工作中的方方面面了。
Now, I have done this many times, believe me and the breaking point is not always at the same mass.
这个我做过无数次，相信我，开始加速需要的质量并不总相同。
The formal definition is that the gravitational potential energy at a point P is the work that I, Walter Lewin, have to do to bring that mass from infinity to that point P.
形式定义就是,它在点P的重力势能,等于我，将物体从无穷远处,移动至点P所做的功。
The center of mass of a system is defined as follows: I have here some kind of an object not just a point mass, but it has a finite size.
系统的重心,是这样定义的：,我有一个物体,不是有棱角的物体，但它大小有限。
The other way to think about it, if I had a flat object then the center of mass would basically be the point where I would need to hold it so it is perfectly balanced.
从另一个角度看，一个平面物体的重心就是,如果在重心处拿起物体，它就能完全地保持平衡。
If you are going to push that object that would be really where the equivalent point mass would lie.
给物体一个推力，就等价于推力作用在重心的情况。
In fact, a 1% increase in body mass results in a 0.6 percentage point decrease in family income.
事实上，增加1%的体重会导致家庭收入减少0.6%。
Our brief is to ensure that those of mass destruction are not used, to the point where if they are launched we will destroy them.
我们的摘要是确保那些大规模杀伤性武器没有被使用，直到有一天如果它们被启动，那么我们将毁灭它们。
If all rows in a table are deleted (known as a mass delete), all segments become immediately available for reuse at the COMMIT point, without requiring the REORG utility to be executed.
如果一个表中的所有行都被删除(即massdelete)，则在执行COMMIT之际，该表所有的段就立即可以为其他表所用，而不需要执行REORG实用程序。
The researchers calculated that every extra point of body mass index (BMI – your weight in kilograms divided by the square of your height in metres) led to a 1-point drop in the memory test.
研究人员计算出在记忆测试里她们每超过一个身体质量系数（BMI——身高kg/体重m的平方）值，她们的记忆力就下降一个单位。
The tremendous gravity of the black hole, estimated to have a mass 100 million times that of our sun, then stretched the star to the point of breaking.
黑洞巨大的引力随后把恒星不断拉伸直到破裂，黑洞的引力估计是太阳引力的1亿倍。
Contat also said that the system is production-ready at this point, and it will simply take a manufacturer that wants to add it as an option before it's available to the mass market.
Contat也表示该系统此时已经备产，考虑到纷杂的市场环境，届时它只会选择一个厂商备选配备该系统。
Case in point: Mass Effect 2, which came out in January and sold more than 2 million units in its first week of release.
准确例子：质量效应2，一月份发布，发行第一周销量超200万套。
The origin is located on the axis at the point closest to the center of mass.
原点坐落在转轴上最靠近物体质心的一点。
A theorem on kinetic energy for variable mass-point and formula of work of recoil internal forces are given and the reason of soft-rope query is discussed.
给出变质量质点的动能定理和一对反推内力作功的表达式，并由此给出软绳问题的正确解释。
A theorem on kinetic energy for variable mass-point and formula of work of recoil internal forces are given and the reason of soft-rope query is discussed.
给出变质量质点的动能定理和一对反推内力作功的表达式，并由此给出软绳问题的正确解释。
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