The ladder operator method is used to analyze the solutions to this system's quantum analogue. Ones with a time-dependent external force are driven, while ones with a source of external friction are called damped. These systems famously display both 
The ladder operator method is used to analyze the solutions to this system's quantum analogue. Ones with a time-dependent external force are driven, while ones with a source of external friction are called damped. These systems famously display both linearity and time translation invariance, and their solutions frequently invoke an angular frequency proportional to one over the square root of mass. Springs are common examples of, for 10 points, what system, whose periodic motion centers on an equilibrium position?
The ladder operator method is used to analyze the solutions to this system's quantum analogue.
{harmonic} oscillator