If you're looking for resonators for the strings in Activity 1, cut the bottom out of a foam cup and put it under the string. You can vary the width of the resonator to give you the best sound - I found for the material provided in the kit that a 1/2 in thick resonator works well. We had a couple of the strings set up in adjacent tables and were jammin'...
Great to see such Active use of the activephysicstc. I have found that any coffee cup (styrofoam, cardboard) can be placed beneath the string. As the cup is moved to shorten the string, you can easily hear the change in pitch. I've also found that having people putting their ear in the cup brings big smiles.
