I recently had a lab in physics class that I was a little confused about. I posted a picture of a couple parts of the lab including the instructions and a couple of questions. I also highlighted a few things that confused me. In the instructions it said that all objects vibrate at a set of natural frequencies. What does it mean by set? I thought each object only had one natural frequency. I was also confused by the statement that ressonace occurring increased the volume. I would think that resonance would result in more sound, but not sound with a greater amplitude. Finally can somebody explain the last things I highlighted and explain the two questions at the bottom of the attached image?