======Singing Rod======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Categories:** {{$demo.categories}}
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**Alternative titles:** Resonating Metal Rod
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====Summary====                   
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====Procedure====  
Part 1: Resonance by Striking  
  - Hold a metal rod at its midpoint.  
  - Strike one end against a table or tap it with a hammer.  
  - Listen for the clear fundamental tone.  
  - Hold the rod at one-quarter of its length and strike again.  
  - Observe the change in pitch due to the overtone.  
  - Try holding the rod at different positions to explore resonance and damping.  

Part 2: Singing Rod by Rubbing  
  - Hold the rod loosely at its midpoint.  
  - Rub the length of the rod with fine sandpaper until it begins to resonate.  
  - Adjust the pace of rubbing to achieve a sustained "singing" sound.  
  - Experiment by holding the rod at one-quarter length and rubbing again to produce a higher-pitched overtone.  
  - Ask students where the sound originates and how to stop the vibrations.



====Links==== 
Singing Rod Demo - College Physics with Greg Francis: 
{{youtube>ZjMUn5fecWk?}}\\

Singing Rod - A Cool Vibration Trick - Sick Science!: 
{{youtube>qQgP9zG681g?}}\\

📄 Singing rod - Ad Mooldijk & Norbert van Veen: [[https://interactivetextbooks.tudelft.nl/showthephysics/demos/demo81/demo81.html]]\\

====Variations====
  * Compare rods of different materials (aluminum vs brass) and lengths.  
  * Use a hammer instead of sandpaper to excite vibrations.  
  * Record frequencies with a smartphone spectrum analyzer (e.g., phyphox).



====Safety Precautions====
  * Ensure the rod is held firmly to avoid dropping it.  
  * Keep the sound duration short, as high-pitched tones can be uncomfortable.




====Questions to Consider====
  * Why does holding the rod at the midpoint produce the fundamental tone? (It creates a node at the center and antinodes at the ends.)  
  * What changes when you hold the rod at one-quarter length? (It produces the first overtone, an octave higher.)  
  * Is the vibration longitudinal or transverse? (Both can occur; damping the rod differently reveals each type.)  
  * How can the speed of sound in the rod be calculated from its frequency and length? (Using the relationship between wavelength, frequency, and wave speed.)