A Roller Coaster Ride through Relativity/Appendix H

The Gravitational Potential at the surface of a starEdit

Gravitational Potential

The force of gravity on a mass m at a distance r away from a star of mass M is equal to:


The work done in pulling the mass from the surface of the star out to infinity is therefore:


This works out to be


and therefore the gravitational potential difference Δφ between the surface and ∞ is


Now by definition, the gravitational potential at ∞ is zero so the potential at the surface is negative, hence:


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