Impossible escape velocity question

AI Thread Summary
The discussion revolves around calculating the escape velocity for a hypothetical celestial object with the same density as the sun. It is established that escape velocity cannot be determined without knowing both the density and the radius of the object. The formula v = 8.873 x 10^-4 x r indicates that radius is essential for calculating escape velocity. Participants agree that if the question assumes the same radius as the sun, the answer would be option B. Ultimately, the necessity of additional parameters for a valid calculation is emphasized.
infirmus
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I've got a question in front of me that asks to find the escape velocity for a hypothetical celestial object that has the same density as the sun.

MC answers are -
1)2.51 x 10^3 m/s
2)6.18 x 10^5 m/s
3)3.08 x 10^5 m/s
4)5.42 x 10^10 m/s

As far as I can work out its not possible to find an escape velocity while only knowing the density. I can work out that

v = 8.873 x 10^-4 x r

but not find actual v without knowing the radius.
 
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You are right. The "escape velocity" depends upon the mass not the density.

If you are not given the radius of the object as well as the density, you cannot find the mass.
 
infirmus said:
I've got a question in front of me that asks to find the escape velocity for a hypothetical celestial object that has the same density as the sun.

This is a silly question (on their part). If they want you to also assume that it has the same radius as the sun, and you do need a radius to solve this problem, then answer is B. If that is what they want, though, they might as well have asked what the escape velocity from the surface of the sun was.
 
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