Now this is when I want to stop for a second and I know that some of you, from past experience, are somewhat math phobic.
现在我们暂停一下,根据之前的教学经验,我知道有些人有数学恐惧症
This is what's called the Bohr radius, and we'll explain - hopefully we'll get to it today where this Bohr radius name comes from, but for now what you need to know is just that it's a constant, just treat it like a constant, and it turns out to be equal to or about 1/2 an angstrom.
它叫做玻尔半径,我们后面会解释,希望我们今天可以讲到,波尔半径这个名称的由来,但现在你们只要记住,它是一个常数,只要把它当做一个常数对待,它等于,或者是1/2埃。
Now you have to know from elementary calculus that v times dv/dt is really d by dt of v square over 2.
根据初等微积分知识你们得知道,v乘以dv/dt其实就是d/2)/dt
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