Singing Aluminum Rod

Rod produces a loud eerie tone. Ask students to predict what will happen. Hold at center and rub/slide fingers along rod. Key idea: Friction excites a resonant longitudinal vibration mode. Ask: Where is the rod moving if we can barely see it? Safety and cleanup: Teacher demo; keep rod clear of faces. https://www.youtube.com/watch?v=bnsCqG7GlB8