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IYPT 2010 Vienna

IYPT 2010 Vienna. FRANCE. FRANCE. Problem 12. Wet towels. When a wet towel is flicked , it may create a cracking noise like a whip . Investigate the effect. Why does a wet towel crack louder than a dry one?. Questions. What is the origin of the cracking noise?

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IYPT 2010 Vienna

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  1. IYPT 2010 Vienna FRANCE FRANCE

  2. Problem 12. Wettowels • When a wettowelisflicked, itmaycreate a cracking noise like a whip. Investigate the effect. Why does a wet towel crack louder than a dry one?

  3. Questions • Whatis the origin of the cracking noise? • Whatis the movementthatpermits the end of the towel to reach a veryhighvelocity? • Whatparameters of the towel are important in thisphenomenon?

  4. The origin of the sound 30 images/s • It is not a collision thatcreates the sound • the end of the towelreaches a highvelocitysothereis a bigdifference of pressure in the air and a cracking noise isproduced

  5. Measurement of the velocity Camera: 1000 images/s • With the software imageJ: • measurement of the velocity of the end of the towel

  6. measurement • thereis a peak of speed >100m/s

  7. Orientation of the speed x V Vy y Vx • the peak of speed isratherhorirontalthan vertical

  8. The speed of the hand

  9. Whatmovementcanbringsuch a velocity?

  10. The sollitonaccelerates

  11. The dynamic of the movement

  12. Wettowel/dry towel amplitude as a function of time for several cracking noises DRY WET

  13. Conclusion

  14. frequencies amplitude Recording of the cracking noise Time (s) amplitude Frequency (kHz) no well-definedfrequency

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