来自《耶鲁大学开放课程：基础物理 第7集 第7集》
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And the constants--这个常数 -
One of the purposes of a constant is常数的作用之一就是 -
to make the dimensions come out right;保持量纲一致 -
the other is to make the values come out right.另一作用就是使数值正确 -
Because I got to make sure that因为我要确定 近地条件下 -
when I apply it to an apple near the Earth,如果对一只苹果用这个公式 -
I put the mass of the apple,代入苹果的质量 -
and let's say I divide by the apple.让我把苹果质量除过来 -
This whole thing, what should it be equal to?这整个式子等于多少呢 -
It's got to be 9.8, you understand that?就等于 9.8 明白吗 -
The acceleration of the apple,苹果的加速度 -
near the Earth, has to be 9.8.近地条件下 只能是 9.8