Suppose we have a damped harmonic oscillator and we also apply an external force such that our system oscillates in steady state. If the frequency of my force matches the natural frequency of my oscillator, I will have resonance. However, I've also read the description of resonance as the unidirectional flow of energy from the external force to the oscillator. Can anyone explain what this exactly means and how?
Also, I've read other posts here, where they use fourier transform of force while deriving x. I have no idea why Fourier transform is used here, and how does it make the calculations any simpler. Please illuminate me on this!!