The essential prerequisite for using lever scale is that its maker knew the principle well.

不等臂天平的出现，其前提条件是制造者对杠杆原理的掌握。

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The essential prerequisite for using lever scale is that its maker knew the principle well.

不等臂天平的出现，其前提条件是制造者对杠杆原理的掌握。

youdao