Forced Damped Vibration: Phasors
A solution of the ODE representing a driven spring/mass/dashpot system represents a balance of forces. If the driving force is sinusoidal, these various forces also vary sinusoidally, and the balance may be represented using phasors (i.e. complex numbers).
![](https://mathlets.org/wp-content/uploads/forced-damped-vibration-phasors.jpg)