A Roller Coaster Ride through Relativity/Appendix H
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![](//upload.wikimedia.org/wikipedia/commons/0/02/GravitationalPotential2.png)
Gravitational Potential
The Gravitational Potential at the surface of a star
[edit | edit source]![](http://upload.wikimedia.org/wikipedia/commons/0/02/GravitationalPotential2.png)
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: