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Homework Help: Explain how the "snap" of a wet towel is produced

  1. Nov 18, 2005 #1
    1) Explain how the "snap" of a wet towel is produced
    2) Describe how a bat uses sound to find its way around
    3)Why is is difficult for an aircraft to break through a sound barrier?
    if anyone can answer these questions it would be alot of help. THANK
  2. jcsd
  3. Nov 18, 2005 #2


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    Gold Member

    The 'snap' of a wet (or dry) towel is the same as the 'crack' of a whip. It's a miniature sonic boom from the tip exceeding the speed of sound.

    A bat navigates by sonar in the same manner as cetaceans. It's similar to radar, but based upon sonic waves rather than electromagnetic ones. The bat emits high-frequency sound from its vocal chords, then those honkin' huge ears collect the echos and its brain calculates the distance to something based upon the time delay. It's amazingly accurate, allowing the bat to 'see' something as small and fast-moving as a gnat.

    A plane has to have the right sort of shape, as well as power, to break the sound barrier because air is very much like a solid object at that sort of speed. Transonic shockwaves will batter the daylights out of a poorly designed craft. A properly designed one doesn't actually have any difficulty passing 1 Mach.

    I love your username; a picture in the Members' Photo section is indicated. :biggrin:
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