Thanks for the response. It's not a homework question - just a problem I thought was interesting.
Let me digest what you've suggested and I'll get back with some clarification questions.
Hi. Here's my problem, stated with more detail.
Imagine a cylindrical cup of coffee, being stirred and where the surface of the stirred coffee has reached some steady state. In terms of the rate of rotation of the liquid and its density, define the equation of the surface of the rotating liquid...
my first post having just joined!
Problem statement - what curve describes the surface of a rotating liquid? Stirring my cup of coffee years ago sparked this thought.
Question - is the way to solve this problem to use variational calculus, or fluid dynamics? I have always thought the former but...