1. The problem statement, all variables and given/known data A body of unknown mass is attached to an ideal spring with force constant 123 N/m. It is found to vibrate with a frequency of 5.65 Hz. Find the mass of the object. 2. Relevant equations F=-kx F=ma No idea what else... 3. The attempt at a solution No idea where to start. I get to: ma=-kx m = (-123x) / (a) and can't think where to go from there. I've tried: 1cycle=4 max displacments (x), so f=5.65Hz = 22.6 cycles of x /s thereby returning x as .25, but that's dead wrong. Any ideas? I'm totally lost.