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Do Bullets Fly, or Glide?

  1. Dec 25, 2011 #1
    I always hear people talk about "flying bullets," or other things for that matter...baseballs, squirels, etc. But correct me if I'm wrong, these objects are just gliding. Flying refers to self-propulsion. I know that the term is used loosely, maybe by a sportscaster saying "look at that football fly". But technically speaking, this is an incorrect use of the word. Anyone want to clarify?
     
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  3. Dec 25, 2011 #2

    I like Serena

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    According to wikipedia, flying is: "The act or process of flight".

    And: "Flight is the process by which an object moves either through an atmosphere (especially the air) or beyond it (as in the case of spaceflight) by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement."


    So it's an interesting distinction, but it seems to me that "flying bullets" fit the definition of flying (as far as wikipedia is concerned).
     
  4. Dec 25, 2011 #3

    Danger

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    Welcome to PF, Fellow.
    Wikipedia is not always your friend, but I won't argue this point with it.
    My observation is based upon the OP parameters. Footballs, bullets, baseballs and bullfighters do not fly or glide; they follow ballistic paths. Squirrels (of one type) and human hang-glider pilots glide; they are to some extent responsible for their flight paths, but are not powered. Birds and aeroplanes with engines fly. They have self-contained propulsion systems as well as manoeuvring controls.
     
  5. Dec 25, 2011 #4

    NascentOxygen

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    To me, glide implies wings or a shape that derives lift from passage through air or water. Fly implies the provision of a means of propulsion. Bullets are not shaped to generate an upward lift, and, having exited the barrel, follow a path entirely dictated by gravity (if we overlook air resistance). This is close to what we call fall. They seem to be similar to an arrow; the spin around their longitudinal axis there to maintain heading.

    I'm undecided about a golf ball, or cricket ball. These can be spun so as to generate lift or to curve sideways, so maybe they trade some rotational energy for lift or course alteration? It's not so much a propulsion (forward thrust) as a form of active glide.
     
  6. Dec 25, 2011 #5

    Danger

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    That is a very good point that I never considered before. At what point does spin change a ballistic path to a glidepath? Hmmm... I must admit to being totally perplexed by this. I really hope that one of the aeronautical engineers or physicists can address the question soon.
     
  7. Dec 25, 2011 #6
    Back when I was "flying" sailplanes (gliders), I once managed to remain aloft for 5 hours and 12 minutes. I had to work my tail off to do that, and all the while I was under the impression that I was flying. I've circled in thermals with birds (turkey vultures), seemed to me that the birds (who were not flapping their wings at the time) and I were all flying. Right?
     
  8. Dec 26, 2011 #7

    Danger

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    I can only reference my previous statement. Sailplanes are called 'gliders' because they glide. So do several species of birds, primarily of the raptor variety, although they are capable of powered flight and their gliding is frequently called 'soaring'. You can also buy sailplanes that have emergency engines. Once you unfurl the pylon and fire that sucker up, you are flying; until then, you are gliding.
    Regardless, a bullet absolutely does not 'fly', which was the essence of the original post. To suggest so would also suggest that a bowling ball 'flies' when dropped off of a roof.
     
  9. Dec 26, 2011 #8
    A bullet leaving the barrel of a gun does not fly, in fact if you were to drop a bullet from the same height as a bullet leaving a gun. Both bullets will still fall to the ground at exactly the same time.
     
  10. Dec 26, 2011 #9
    I suspect we are locked into an unsolvable game of defining a vague word. I'll close with one final shot at this.

    Soaring birds and soaring sailplane pilots don't just glide around, they use solar fuel plus intelligence to stay up. That solar fuel, the energy that fuels thermals (updrafts), is the same fuel that powers a Piper Cub, via old plants and animals that have been transformed into petroleum/aviation gas. I think you are being technically over-picky by defining flying by how this fuel is used/converted. In my view, use of solar energy to roam around in the sky is what flying is all about.
     
  11. Dec 26, 2011 #10

    D H

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    Most of you (oldfart excluded) are being far too pedantic. The question was about language, not science. You are flying in the face of common usage. Bullets fly. It's right there in my dictionary ("bullets flying in every direction"). You can fly a flag, fly a kite, fly an idea, fly out to left field, fly blind. A door can fly open, as can your fly. Birds, airplanes, spacecraft, bullets, and even time can fly by.

    Words have multiple meanings.
     
  12. Dec 26, 2011 #11

    Danger

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    DH, do you consider yourself to be flying when you jump off of a diving board, just because you manage to stay dry for a couple of seconds? That's the same thing that happens to a bullet once it leaves the muzzle.
     
  13. Dec 26, 2011 #12

    NascentOxygen

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    If you were peddling furiously then possibly you were flying. :smile:

    But I would opine that you were falling, unerringly descending with reference to the air about you. Not in freefall, though, because your wings were deriving lift from the air under the wings you as you passed through it. At times you would have traded forward speed to rise faster than the air currents, but there is no escaping that the rolling average indicates a pattern of constant descending, relative to the medium you were moving in.
     
  14. Dec 26, 2011 #13

    D H

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    It depends. Suppose someone is pursuing me. I see a diving board and jump off it as a means of evading my would be captor. One could say that "D H flew through the yard and then flew off the diving board to avoid capture." Or suppose that as a stunt, someone tosses a hotdog so that it reaches me just as I leave the board. I catch and eat the hotdog midflight and finish the dive in grand style. One could then literally say that "D H ate lunch on the fly."


    You who are arguing that bullets don't fly because bullets don't have wings or some other means of propulsion are being overly pedantic. You are projecting the scientist's and engineer's need for one precise definition onto the public at large.

    The term "bullets flying in every direction" is very old. Here's an article written near the onset of the American Civil War that uses that exact phrase: http://www.nytimes.com/1861/05/13/news/highly-important-from-missouri.html. I suspect that this particular use of flying bullets is nearly as old as bullets.
     
  15. Dec 26, 2011 #14

    russ_watters

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    I'm not so sure - though I'd find it odd to visit a science site in search of a figurative definition - but in either case, that's a question for the OP:

    fellow26, do you want a scientific or figurative answer? From the dictionary, DH is clearly right that as a figure of speech, the word "fly" is used very loosely and can describe a great number of actions (only 3 of 12 definitions are scientific in nature). But from a scientific point of view, only the first two definitions apply:

    1. to move through the air using wings.
    2. to be carried through the air by the wind or any other force or agency: bits of paper flying about.

    A bullet fired from a gun does not "fly" according to those two definitions. The key factor being that it does not utilize the air to generate lift.
     
  16. Dec 27, 2011 #15
    Flying usually infers the generation of lift and bullets don't. Bullets actually wobble, more than they fly.
     
  17. Dec 28, 2011 #16
    Ah ha, I like that you use the word "actually". How would you quantify "wobble" and "fly" to calculate that "wobble" exceeds "fly"?

    I think we all know what the OP is getting at. So why doesn't the "flight race" determine what flying is. I'm sure there would have to be something along the lines of x height for x distance over x time, and then something to do with propulsion.

    Fundamentally, anything that looks like it should fall and doesn't is "floating", if it has direction it's flying. Clouds float, and on windy days they fly. :rolleyes:

    Thanks D H for your posts. Helped me understand semantics better.
     
    Last edited: Dec 28, 2011
  18. Dec 28, 2011 #17

    Dale

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    Not the public at large, just PF :smile: I think that is probably acceptable here.
     
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