Impossible escape velocity question

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SUMMARY

The discussion centers on calculating the escape velocity for a hypothetical celestial object with the same density as the Sun. Participants conclude that escape velocity cannot be determined solely from density; the radius of the object is also required. The formula provided, v = 8.873 x 10^-4 x r, indicates that without knowing the radius, the mass—and thus the escape velocity—remains unknown. The correct answer, assuming the radius is equal to that of the Sun, is option B, which corresponds to the escape velocity from the Sun's surface.

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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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