I am currently compiling, solving, and adding complexities to problems involving strings in physics. The scope of my work covers basically everything: from introductory physics to string theory. I'm looking for any suggestions for problems and any way to add complexities to a given problem. I've spent a while finding, solving, and typing some up in LaTeX but I would like to find as many as possible. A few examples that I have already done are the brachistochrone (though it isn't really a "string problem"), the vibrating string (including a discussion of the various boundary conditions), the boat problem (from David Morin's Classical Mechanics book), the relativistic string (incomplete, barely started), the Atwood machine, the simple pendulum, among others (which I really just wrote down). Some examples of added complexity are elasticity, variable density, etc. I welcome any suggestions for more problems (especially if they come with the title of the book in which they are posed), as well as ways to add complexity. The only stipulation is that they must involve strings (ie the physics must be "tied" to the string in some important way). Thanks for any suggestions!