So we're studying resonance. It says that it occurs when an external periodic force acting on a body is exactly equal to the natural frequency of the body. The body then begins to vibrate with greater/increasing amplitude and intensity. And so what I want to know is that is there a difference between the type of resonance that occurs in a vacuum and the type in a medium (say water) ? Like in a vacuum, would a pendulum experiencing resonance continue to complete oscillations, or would it spin all the way around or something?