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He said, first, let it go a little distance, take the distance over time, that gives you the velocity now.
他说,首先,让它运动一小段距离,距离除以时间,你就能得到现在的速度
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One way is to say, if I do a full revolution, I think of the speed as a distance over time.
一种方法是,如果我转完整的一圈,我认为速度就是距离除以时间
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So, for example, if I have a sodium ion over here, and I have a chloride ion over here, where the distance from center to center r I'm denoting as r, this is nucleus to nucleus separation.
所以，比如这有一个钠离子，和一个氯离子，它们中心与中心间的距离,我把它设为，这是原子核和原子和的间距。
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And so, we walk that distance from Pierson College down to the York Street Gate, over to Chapel Street, make the left on Chapel Street, another block down to High walk into the Starbuck's.
然后，我们从皮尔逊学院出发,沿着约克街走，越过新教堂街，向左转，又穿过一条街道,走到星巴克。
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And the telephone companies in the United State, generally about 200 billion dollars a year carrying long distance telephone conversations and they thought this conversations might be carried for free over the internet was quite shocking to them. Of course free is very low price, and they are not like it to be free.
美国的各电话公司，一般大约有每年2千亿美元,来自长途电话会话，他们认为,这些会话有可能通过互联网免费传输,对他们来说是相当震惊的，当然了,免费是很低的价格了，他们不希望它免费。
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So this is a - c over b and this is a - c over 2b so this distance and this distance are meant to be the same.
这点是,/b,这点是,/2b,这两段长度应该是相等的
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The period, that's right. So, it's going to take one period to move that long. And another way 1 we can say period is just 1 over nu or 1 over the frequency So, now we know both the distance traveled and the time the elapsed.
还是？周期，对的,它需要一个周期的时间,另一种说法是周期是,除以nu，也就是1除以频率,现在我们同时知道了。
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So, we can just plug it in. Speed is equal to the distance traveled, which is lambda over the time elapsed, which is 1 over nu. so, we can re-write that as speed is equal to lambda nu times nu, and it turns out typically this is reported in meters per second or nanometers per second.
经过的距离和所花的时间,我们把它们带进来,速度等于经过的距离,也即是lambda除以,所花的时间,通常它的单位,是米每秒或者纳米每秒。
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