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It knows that this particle happened to have a height of 15, at the time of 0, and a velocity of 10, and it is falling under gravity with an acceleration of -10.
这个质点恰好处在高度为15的地方,零时刻,初速为10,并在重力作用下以-10的加速度下坠
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And this is just a Newtonian expression of momentum, the product of the mass of the electron times its instant velocity.
这只是牛顿学上关于动量的表达，用电子质量,乘以瞬时速度。
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So, if we're trying to figure out the wavelength of a Matsuzaka fastball, we need to consider the velocity first, which is 42 miles per hour.
如果我们尝试计算一个,松阪发出快球的波长，我们首先需要考虑速度，每小时为42英里。
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But things which were at rest will move at a constant velocity, opposite of the velocity that you have relative to me.
这些静止的东西都在匀速运动,方向正好跟你相对我运动的速度方向相反
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Let's plot droplet velocity as a function of looking at the number that have this velocity 0 with the zero being in the center here.
我们将液滴的速度设定为,观察那些数字作用，在中心的地方,速度为。
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So, if we kind of think about the numbers we would need, we would actually need a velocity that approached something that's about 10 to the negative 30 meters per second.
所以如果我们稍微想想，我们需要的数值是多少，我们需要一个,大约为10的负30次方米每秒的速度。
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I would expect, whether you're a Red Sox fan or not, you to be able to look at a list of different pitchers and their average velocity for their fastball, and tell me who has the longest or the shortest wavelength.
无论你是否是一个红袜队球迷，我预想你会看到一系列,不同的投手和他们,投出快球的平均速度，告诉我谁有最长的,或者最短的波长。
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If I gave you the location of a particle as a function of time, you can find the velocity by taking derivatives.
如果我给出物体的位移是时间的函数,你可以通过求导来得到速度
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NO So that the more complete answer to the question is that no, we're never going to be able to observe that because of the uncertainty principle it's not possible to observe a velocity that's this slow for a macroscopic object.
所以这个问题的完整答案是，由于不确定性原理,我们不可能测量到这么慢的,宏观物体的速度，希望这个解释。
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If you took a 15 inch artillery shell moving at the velocity it typically goes at, and take that amount of kinetic energy versus the resistive capacity of a sheet of tissue paper, that's the scale that we're looking at here.
如果你有1个15英寸的炮弹,按照经典的速度移动，会消耗大量的动能,抵抗来自于一张薄纸的阻力，这就是我们在这儿看到的尺度。
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So, we would actually need a really, really, really tiny velocity here to actually overcome the size of the mass, if we're talking about macroscopic particles, to have a wavelength that's going to be on the order.
是10的负34次方焦耳每秒,所以如果我们谈论的是要一个，宏观粒子有相应数量级的波长的话，我们需要一个非常非常非常小的速度来。
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So the Earth is an inertial frame of reference, if you go in a train relative to the Earth at constant velocity, you're also inertial.
所以,地球是一个惯性参考系,如果你坐在相对于地球匀速运动的火车里,你也处于惯性状态
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That's another way of saying maintaining velocity if it's not acted upon by a force.
这就是不受外力作用时,速度保持不变的另一种说法
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Because any velocity I ascribe to a particle or an object, you will add a certain constant to it by the law of composition of velocity.
因为我描述的任何一个质点或者物体的速度,你都要根据速度叠加法则,给它加上某个常数
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It's in the nature of things to go at a constant velocity.
能保持恒定速度是物体的固有性质
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We divide that by the mass, so 0.12 kilograms, that's the mass of a regulation baseball for the major leagues, and the velocity of the baseball is 42 meters per second. So, we can cross out our units doing our unit analysis.
我们用质量来除它，质量为0，12千克，这是大多数联赛规定的棒球质量,棒球的速度为42米每秒,所以，我们可以消去单位,来做单位分析。
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Initial velocity is a pair of numbers.
初速度也是一对数字
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If you want to know how fast it's moving at a given time, if you want to know the velocity, I just take the derivative of this answer, which is 10-10t.
如果你想知道它在给定时刻的运动有多快,如果你想知道它的速度,我只要对这个式子求导,得到10-10t
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take the derivative of this, get the velocity vector and you notice his magnitude is a constant Whichever way you do it, you can then rewrite this as v square over r.
对这个式子求一次导,就能得到速度矢量,你会发现其模长是常数,不管用什么方法,加速度也可以写成 v^2 / r
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Then, to find the meaning of b, we take one derivative of this, dx/dt, that's velocity as a function of time, and if you took the derivative of this guy, you will find as at+b. That's the velocity of the object.
接下来,为了弄清b的含义,我们取它的一阶导数,dx/dt,得到速度作为时间的函数,如果你对它求导的话,你会得到at+b,这就是物体的速度
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