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Could a fish swim faster than sound?

  1. May 28, 2010 #1
    Is it possible for a fish or a bird to swim/fly faster than sound? I mean: no rockets, no free fall, no cheating by tying a string to the ground and using it to violate the conservation of momentum.

    Is it possible to accelerate over the speed of sound using only fins, wings or screws?
     
  2. jcsd
  3. May 28, 2010 #2
    Not possible, the speed of sound is around the speed a bullet is ejected from a gun.
     
  4. May 28, 2010 #3
    Another thing to consider...the speed of sound is much much faster in water, isn't it?

    Edit: looked it up. Approximately 4.5x faster in water.
     
    Last edited: May 28, 2010
  5. May 28, 2010 #4
    well actually a dolphin cant swim that fast, but put it behind a cruise liner or another ship and they can go pretty darn fast. Faster then they're supposed to, by riding on the wake, as there is less drag due to the ship doing the work for the dolphin. So i wouldn't be surprised if they could do it if they were behind a ship that traveled sufficiently faster than the speed of sound. Assuming, that the terminal velocity of water, like that of air, isn't lower than the speed of sound itself.
     
  6. May 28, 2010 #5
    no there's no animal that can break the sound barrier without attaching rockets to it and that would be pretty cool/cruel. I wonder if we could genetically engineer one some day to do that though, maybe convert food in to rocket fuel or instead of flapping wings eject streams of air out the back. I was watching a documentary based on possible animals that could exist on alien planets, they had an animation of a bird firing streams of air behind it to propel itself but I don't think they said it was possible for it to break the sound barrier.
     
  7. May 28, 2010 #6
    Of course it's possible in theory to go faster than the speed of sound under water, but in practice its nowhere near possible for an animal to get going that fast.

    Simon Malzard, but then the water would be traveling, so the dolphin would just be inside water which is traveling faster than the speed of sound.
     
  8. May 28, 2010 #7
  9. May 28, 2010 #8

    mgb_phys

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    I think the point of the question is can you theoretically swim faster than the speed of sound in the medium.
    If swimming involves pushing against a fluid can you do this faster than a 'push' can travel through the fluid?
     
  10. May 28, 2010 #9
    Yes, the molecules are closer together in water, so disturbance travels faster.

    The ship would have to be traveling at 720 Knots to surpass the speed of sound.
     
  11. May 28, 2010 #10
    Maybe not swim faster than sound, but the 'Pistol Shrimp' can move faster than the speed of sound. Its claw closing travels faster than the speed of sound, taking the local pressure to below the vapour pressure of water, causing a cavitation bubble, which it uses to hunt prey.

    Actually, people think this kind of thing could have applications in future fusion technology, the temperatures created as the cavitation bubble collapses are pretty impressive.

    Perhaps not what you were looking for, but quite interesting I think.

    ,Simon
     
  12. May 28, 2010 #11
    I don't think it moves faster than sound because of this action. The entire mass of the shrimp would need to be accelerated to this velocity and the force of the action is not enough to do this.
     
  13. May 28, 2010 #12
    I meant that its claw travels faster than the speed of sound. The cavitation bubble is somewhat similar to a sonic boom in air. The shrimp remains stationary.
     
  14. May 28, 2010 #13
    Yes, that's exactly my point. Does anyone know the answer?
     
  15. May 28, 2010 #14

    Which must explain why thinks sound different underwater?

    I remember what it sound like but it does sound different.

    Or maybe it is because you can't hear the low frequencies because they are reflected away?
     
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