What do you call these problems and where can I find more

[Vriska]

For example - the field due to a thin rod , proving shell theorem, moment of inertia, shape of a metal disk held over a flame, etc..

In all of these you cleverly use infinitismal elements with the appropriate conditions and integrate. I am looking for more of these infinitismal element physics stuff. Well, need not even be physics honestly, . Some applied calculus based physics textbook perhaps?

 

[Buffu]

These problems are there in any electrodynamics/classical mechanics book, but before you do that or if you just want to do vector calculus ( under which these problems are studied ) you need to get a multivariable calculus book.

Moral of the story : Learn calculus of multivariate functions first then you can solve these problems.