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Shrieking Rod

Shrieking Rod. Prof. Chih-Ta Chia Dept. of Physics NTNU. Problem # 13. Shrieking rod A metal rod is held between two fingers and hit. Investigate how the sound produced depends on the position of holding and hitting the rod?. Vibration in rod?. How did you create vibrations in the rod?

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Shrieking Rod

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  1. Shrieking Rod Prof. Chih-Ta Chia Dept. of Physics NTNU

  2. Problem # 13 • Shrieking rod • A metal rod is held between two fingers and hit. Investigate how the sound produced depends on the position of holding and hitting the rod?

  3. Vibration in rod? • How did you create vibrations in the rod? • Three type of vibrations are created simply by hitting the rod: Longitudinal, torsional and flexural vibrations. • Longitudinal and Flexural vibrations are most likely to last longer, but not the torsional vibrations. • What are the resonance conditions for these three vibrations? • What are the speeds of these three vibrations that travel in the rod. How to determine the wave velocity?

  4. Vibration of Rod? • What is the damping effect on the longitudinal and vibrations? Hitting position dependence? Time dependence? • Longitudinal wave damping and flexural vibration damping? Which one is damped fast?

  5. Cylindrical Rod : Longitudinal and Torsional wave Longitudinal wave speed E: Young’s Modulus Torsional wave speed m: Shear Modulus Passion Ratio :

  6. Young’s Modulus Stress: S Longitudinal Strain: St Young’s Modulus: E

  7. Stress, Strain and Hook’s Law Stress is proportional to Strain. Hook’s Law

  8. Shear Modulus The shear modulus is the elastic modulus we use for the deformation which takes place when a force is applied parallel to one face of the object while the opposite face is held fixed by another equal force. Shear Modulus: m

  9. Resonance : When Clamped in the Middle

  10. Speed of wave in Rod

  11. Flexural Vibrations Equation of Motion : (Length L and radius a) clis the velocity of longitudinal waves in an infinitely long bar. The radius of gyration k is defined as above. For the circular rod, k is half the bar’s radius. As for the square rod, k is D/√12.

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