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Physics of cracking a Whip

  1. Jul 17, 2008 #1
    I am curious about how the end of a whip can break the sound barrier and produce the cracking sound. Does the end of the whip borrow elastic energy from the whip or what kind of forces are responsible for this?

    Answers appreciate, thanks.
  2. jcsd
  3. Jul 17, 2008 #2

    Andy Resnick

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    I've never cracked a whip, so I don't know how difficult it is to do. But the energy I (or whomever) put into the end of the whip does indeed travel along he whip to the tail end, which is very light and can thus attain very high speeds.
  4. Jul 17, 2008 #3


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    It has more to do with both leverage and elasticity. As you swing your arm thriough 180o, the end of the whip must also swing through the same arch. But A) the end of the whip must travel much farther to complete its arch, and B) the end of the whip doesn't start moving right away, but you'll notice it does reach the end of the movement at about the same time as your arm. So, when it finally does move, it covers a much greater distance in a significantly shorter time.
  5. Jul 18, 2008 #4
    What I find interesting with whips, is that the end not only breaks the sound barrier, it often EXCEEDS it.

    For the end of a whip to break Mach 1 is common. But could it reach Mach 2, or 3, or perhaps 7?

    Very likely, given the current "state-of-art" with respect to chemical composition techniques to permit high molecular rigidity with ultra-high flexibility.

    One of the problems is that the end of a whip might slap against it's previous whip-section at very high speeds, thus causing significant damage to the very end of the whip, which results in tip-fraying.

    Going off-course here, but in any event a great deal has been learned and subsequently utilized from understanding whips and their accelerative properties.
  6. Jul 20, 2008 #5
    Excellent answer lurch, thank you. Everything you said makes perfect sense and its very succinct too!

    Now all we have to do is figure out how to put a rocketship on a whip end and get a giant to crack it and voila, instant orbit :)
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