On the surface of earth where is calculated by what

On the surface of the earth, weight is calculated by multiplying mass and gravity. Because we know the radius of the Earth, we can use the Law of Universal Gravitation to calculate the mass of the Earth in terms of the gravitational force on an object (its weight) at the Earth's surface, using the radius of the Earth as the distance.

I think this is the question you were trying to ask if not, ill try it again

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we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).