Concepts

Longitudinal standing waves in an aluminum rod, resonance

Overview

An aluminum rod is held at various nodal points and stroked with rosined fingers or gloves, producing a loud sound that lasts a long time. The sound can be amplified by touching the end of the rod to a styrofoam cup.

Details

Equipment

• [1] Aluminum rod
• [1] Rosined gloves
• [1] Bag of rosin powder
• [1] Solid resin
• [1] Styrofoam cup

Important Notes

• This demonstration requires a lot of advance practice.

Script

1. Wear rosined gloves and add more rosin powder as necessary.
2. Pinch the rod between two fingers at the L/2 location.
3. Stroke the rod firmly starting at L/2 all the way to the rod's end. The rod produces the first harmonic.
4. Press the end of the rod to a styrofoam cup after it has been excited to amplify the sound.
5. Repeat step 2 to 4 while pinching the rod at the L/4 and then L/6 positions to produce the second and third harmonic respectively.

Additional Resources