Lagrangian Method-- 1st form? Zwangskraefte? Mechanics will be the death of me. For some reason, I can do E&M, and particle stuff, but give me a pendulum, and I'm dumbfounded. THat said, I'm working on some problems using Lagrangians, and the only book I have available to me is Goldstein (which is a bit above where I'm at, but helpful, once it clicks). The course I'm taking will count as my uppper level, undergrad mechanics course. Anyway, I've got a problem. Supoose you have a particle that's moving frictionless in a gravitational field on the inside of a paraboloid (which is described in cylindrical coordinates as r= az. How do I come up with the Lagrangian for this? If given one, I can usually figure out more on how to solve this, but it's stumping me. And another thing, I can't figure out what the english term for 'zwangskraft' would be, forced force? I'm supposed to find the size and direction of these forces, but I'm not really sure what it means. Eeep. There's a note saying that I'm supposed to make it a requirement that energy and rotational momentum are conserved. THat isn't heling me at all. Suggestions? ANy other suggestions for texts (that aren't too expensive), that might help me? My exam is in 3 weeks, and I'm lost.