Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

# Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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Harmonic Motion
Waves
Acoustics
Instruments
Sonometer
Open / Closed Resonance Tube
Resonant tunning fork
video  - Dancing Flames (Ruben's Tube)
video  - Air Driven Organ Pipe
Singing Tubes and Rods
video  - Breaking a Wine Glass

### Open / Closed Resonance Tube

#### Purpose:

Demonstrate the acoustic resonance effect in air columns of different length.

#### Procedure:

The Economy Resonance Tube instruction manual describes some details on how to use the tube. Each tube is about 1.3m long, but can slide to different lengths. While in closed tube configuration, experiments can be done with tube lengths as short as 3cm.

Set up the resonance tube in horizontal orientation on its pair of black plastic stands. Place a PASCO open speaker an inch away from the tube opening and connect the speaker to a PASCO function generator.

The resonance tube apparatus can be used as a completely open end tube (open configuration) or with a plug (closed configuration).

Change the speaker frequency and/or tube length to hear the resonances.

Open configuration tube resonates at about 120Hz. The loudest resonances for the closed configuration seems to be between 200 and 400 Hz.

The setup comes with a built-in ruler that allows quantitative measurements as well.

#### Hints:

Open Tube
• 1st Harmonic: f=v/2L
• 2nd Harmonic: f=v/L
• 3rd Harmonic: f=3v/2
Closed Tube
• 1st Harmonic: f=v/4L
• 3rd Harmonic: f=3v/4L
• 5th Harmonic: f=5v/4L

#### Equipment:

• Speaker
• Resonance Tube
• Wave Generator