But gravity has a remarkable property that the pull of the Earth is itself proportional to the inertia of the object.

重力有一个显著特征,即地球的引力,与物体的质量成比例

耶鲁公开课 - 基础物理课程节选

Other is gravitational mass, which is the measure of how much you're attracted to the Earth.

另一个是引力质量,它可以用来衡量地球对物体引力的大小

耶鲁公开课 - 基础物理课程节选

You cannot tell the mass, because what you are doing now is appealing to the notion of mass as something that's related to the pull of the Earth on the object.

你无法测出质量,因为你现在所做的是把质量,用地球对物体的引力给替代了

耶鲁公开课 - 基础物理课程节选