code: def _linearEOM(y,t,pot):
      
      return [y[1],_evaluatelinearForces(pot,y[0],t=t)]
docs: NAME:
         linearEOM
      PURPOSE:
         the one-dimensional equation-of-motion
      INPUT:
         y - current phase-space position
         t - current time
         pot - (list of) linearPotential instance(s)
      OUTPUT:
         dy/dt
      HISTORY:
         2010-07-13 - Bovy (NYU)