Hollow Sphere

  • Thread starter PSOA
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  • #1
PSOA
How do I get rid of infinitesimal mass element dm?
 

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  • #2
radou
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How do I get rid of infinitesimal mass element dm?

I assume you're trying to derive the moment of inertia of a hollow sphere, but you should really be more specific when posting questions.
 
  • #3
PSOA
I am not determining the moment of inertia. I didn't specify what I was doing because I just wish to know of to solve this particularly problem. How to get rid of dm?
 
  • #4
BobG
Science Advisor
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Your differential mass is the rate of change in the mass. It will depend on the object's density (g/cm^3, kg/m^3, etc).

In your case, you have a hollow sphere, so the mass will change in relation to the area (assuming the sphere has an infinitely small thickness). That would be g/cm^2, kg/m^2, etc.

That should allow you to change your variable to dr, the differential radius, since the volume and/or the area will depend upon the radius.
 
  • #5
PSOA
But I need the constant sigma M/A (equivalent to density) which I do not know.
 
  • #6
769
15
Maybe Integrate? I don't really understand your problem.
 
  • #7
PSOA
I need to [tex]\int dm[/tex] for a spherical shell.
 
  • #8
OlderDan
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I need to [tex]\int dm[/tex] for a spherical shell.

Look at the thread that started this.
 
Last edited:

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