I'm having a tough time with a simple problem- the resonant oscillation of a vertical cantilever immersed in a viscous fluid. I have, from Roark's tables, the oscillation frequency for a cantilever with both a concentrated tip load and distributed load: ω=1.732√[(EI*g)/(WL3+0.236(wL4)] But I don't understand why (other than dimensional arguments) why there is 'g' in the numerator. For example, why is 'g' still relevant for a vertical cantilever immersed in a neutrally-bouyant viscous fluid (should g -> Δρ g?). The AFM literature (that I've found) for immersed tips isn't particularly informative. Roark's book doesn't provide any derivation information... any hints/tips/references are gratefully appreciated.