Question

absolute potential at centre of earth is equal to ​

Answer 1

Answer:

As pointed out by an earlier writer, potential energy in a Gravitational field can be measured relative to another reference. But he is wrong to say infinity was used arbitrarily as the absolute zero potential energy reference point. He is also wrong to say that Gravitational PE is negative only by convention. I'll address both separately below.

• Gravitational PE (GPE) is positive when you're “higher up” in a Gravitational field, ie further from the centre of mass. Explanation: work done is a dot product of force and displacement. When moving an object against gravity, the force and displacement are in the same direction, ie away from the centre of mass, so the work done is positive. That means GPE is more negative when a body is nearer the centre of mass. This is because gravity is an attractive force.
• In seeking an absolute reference point, it is important to have something that is universally constant. In a Gravitational field, GPE is more negative when the body is nearer to the centre of mass of the planet, say, and proportional to the mass of the planet. The nearest you can get is the surface of the planet, and the denser the planet, the more negative the GPE. Although there is an absolute minimum distance, there is no absolute maximum mass/density, theoretically. Hence, there is no absolute minimum GPE. So we'll have to set an absolute reference point in the opposite direction, ie away from the centre of mass. Hence, the theoretical absolute maximum GPE is the furthest from every possible Gravitational field. Using that maximum GPE point for reference, everywhere else therefore has negative GPE.