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Why should the amount by which you're attracted to the Earth be also a measure of how much you hate acceleration?
为什么物体受地球引力的大小,恰好能衡量物体加速的难易程度呢
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So, a massless body cannot have a net force on it, because the acceleration of the rope cannot be infinite.
所以没有质量的物体不会受到力,因为绳子的加速度不可能是无穷大
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You will learn in 8.02 that if you have a charged body changing direction, that constitutes an acceleration.
你们将在8。02中学到,如果一个带电体改变方向时，产生一个加速度。
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The government has liberized the economy and that has of course been playing a role but the growth acceleration started almost a decade before that, so the factors are a little more complex.
印度政府让经济自由发展,这一决策显然是起了作用的,但在这一决策出现约10年前,印度经济的加速发展便开始了,所以经济腾飞的原因还比较复杂。
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You cannot have a spring pulled only at one side, because then it will then accelerate with infinite acceleration in that direction.
你不可能对弹簧只施加一边的拉力,因为那样的话弹簧就会以无穷大的加速度加速,就在这个方向上
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Now I can measure that, because I pull it by one centimeter and I find the acceleration it exerts on a known mass.
现在就能测量这个力了,因为把弹簧拉伸 1 厘米,我就知道它让一个质量已知的物体产生的加速度
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When you're falling to the surface of the Earth, you are describing a problem of constant acceleration.
当你讨论下落问题时,你在描述一个加速度恒定的问题
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It says that, "If a body has an acceleration, then you need a force and the relation of the force to acceleration is this thing."
它是这么说的,"如果一个物体有加速度,那么你需要有一个力,力和加速度的关系是这样的"
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A limited class of problems is one in which the acceleration is just a constant.
在这类有限的问题里,加速度均为常数
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We all have a good intuitive feeling for what acceleration is.
我们都对于加速度有一定的感觉
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The advantage of introducing that guy is that if you like, I can now write an equation for the acceleration as a vector.
引入它的好处是,如果你愿意的话,我可以把加速度写成矢量形式
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In other words, you don't have to be moving actually in a circle to have the acceleration.
也就是说,你不必真的在一个圆上运动以获得相应的加速度
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If every time I get the same acceleration, I'm convinced this is a reliable spring that is somehow producing the same force under the same condition.
如果每次都能得到相同的加速度,这个弹簧的可靠性就能令人信服,即它在相同的条件下能够产生相等的力
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Force causes acceleration and this is a precise statement.
力产生了加速度,这是一个精确的说法
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You cannot say to me, "Take a force, due to a spring, and see what force it applies and divide by the acceleration and get the mass, " because we haven't defined force, either.
你不能说,"给弹簧施加一个力,看看它能提供多大的力,然后除以加速度,得到质量",因为我们还没给力下一个定义
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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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We can be precise about how much bigger by saying, "If the acceleration of a body to a given force is ten times that of a one kilogram mass, then this mass is one-tenth of one kilogram."
我们能精确地知道质量能大多少,只需要说,"如果物体在给定力作用下的加速度,是一个 1 千克物体的加速度的 10 倍,那这个物体的质量就是 1 千克的十分之一"
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If your plan is to accelerate a 3 kg mass with an acceleration of 2 meters per second, you better have a rope that can furnish that force and it can take the tension of 6 Newtons.
如果你想用 2 米每秒平方的加速度,去拉一个 3 千克的物体,那么你就需要一根能提供拉力的绳子,并且它能够承受 6 牛的张力
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That's how by either balancing the unknown force with a known force or by simply measuring the acceleration as I fall towards this podium and multiplying by mass, you can find the force that exerts on me.
我们既可以让未知力与已知力平衡,也可以只测量我冲向讲台时加速度的大小,再与我的质量相乘,都能求出作用在我身上的力的大小
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A typical problem that you may have done in your first pass at Newton's law, someone tells you a force of 36 Newtons is acting on a mass of whatever, 4 kilograms; what's the acceleration?
在你们第一次接触牛顿定律时,可能见过这么一道典型题目,告诉你,一个 36 牛的力,作用在一个物体上,4 千克吧,问加速度是多少
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I want to consider a particle which has definite acceleration a, a constant one, but a is now a vector.
我想考虑一个加速度为 a 的质点,加速度恒定,但 a 是一个矢量
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When a particle moves in a circle, it has an acceleration towards the center of this size, v^2 over R.
当一个质点在圆周上运动时,它有一个指向圆心的加速度,v^2 / R
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You're only given the particle has acceleration a, and you are asked to find out what is x?
你只知道质点的加速度为a,你需要求出x是多少
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That means the acceleration is pointing towards the center of the circle and it has a magnitude a.
也就是说加速度,始终指向圆心,其模长为 a
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So what I'm saying here is we are specializing to a limited class of motion where the particle has a definite acceleration, a.
我在这里想说的是,我们正在专门讨论一类问题,这些问题中,质点都有一个确定的加速度a
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It tells you when a particle moves in a circle, it has an acceleration in a negative R direction, namely directed towards the center.
它告诉你当一个物体在圆周上运动时,它有一个在 -R 方向的加速度,也就是说是直接指向圆心的
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You can easily check by taking two derivatives that this particle does have the acceleration a.
你可以很容易地通过求两次导来验证,这个质点的加速度确实为 a
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