Removing Infinitesimal Mass Elements from a Hollow Sphere

[PSOA]

How do I get rid of infinitesimal mass element dm?

 

[radou]

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.

 

[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?

 

[BobG]

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.

 

[PSOA]

But I need the constant sigma M/A (equivalent to density) which I do not know.

 

[billiards]

Maybe Integrate? I don't really understand your problem.

 

[PSOA]

I need to $$\int dm$$ for a spherical shell.

 

[OlderDan]

I need to $$\int dm$$ for a spherical shell.

Look at the thread that started this.