Newton's law of gravity; Gravitational force from a shell; Hooke's 'law'.

克普勒圆周轨道第三定律；利用积分推导球壳的引力；弹簧。

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Electronic scale weighing instrument, belonging to a, is the use of Hooke's law or the force of the lever balance principle to measure quality tools.

电子秤，属于衡器的一种，是利用胡克定律或力的杠杆平衡原理测定物体质量的工具。

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