- 1,642

- 2

I'm not understanding this integral quite fully. Of course G is the constant and rho is also a constant since the sphere is homogeneous. And pi*r'^2 dr' gives the area of circle with respect to r' with limits of a and b. However, I'm not understanding how theta comes into it and the ignoring of phi. I understand the rest of the derivation.

Of course, the integral from a to b of pi*r'^2 dr' gives an area for the annulus in the plane. I guess I'm having trouble seeing the three-dimensional derivation.

http://i111.photobucket.com/albums/n149/camarolt4z28/2010-10-03144234.jpg?t=1286135265 [Broken]

http://i111.photobucket.com/albums/n149/camarolt4z28/2010-10-03144253.jpg?t=1286135285 [Broken]

Of course, the integral from a to b of pi*r'^2 dr' gives an area for the annulus in the plane. I guess I'm having trouble seeing the three-dimensional derivation.

http://i111.photobucket.com/albums/n149/camarolt4z28/2010-10-03144234.jpg?t=1286135265 [Broken]

http://i111.photobucket.com/albums/n149/camarolt4z28/2010-10-03144253.jpg?t=1286135285 [Broken]

Last edited by a moderator: