I heard that the driving force, for resonance, has to be π/2 out of phase with the displacement curve of the driven object. This was because the velocity curve is also π/2 out of phase with the displacement curve. However, what if the two are π/2 in the opposite direction, resulting in antiphase?
I think this means that the system is heavily damped, but I heard that this π/2 thing was a general rule but this here seems to be an exception. Is the rule therefore simply that the driving force has to be in phase with the velocity curve of the driven object?
And actually passed?