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Tricky question

  1. Feb 13, 2007 #1
    A man flies a small light aircraft straight and level. Inside the cockpit is a fly flying. Does the fly’s weight contribute to the aircraft’s weight at all?
     
  2. jcsd
  3. Feb 13, 2007 #2
  4. Feb 13, 2007 #3

    dextercioby

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    Of course not, unless the fly is attached to the walls of the plane (probably dead in the process)
     
  5. Feb 13, 2007 #4

    daniel_i_l

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    actually, even if the fly is flying, it still contributes to the weight of the plane - because inorder to stay in the air it has to push down with it's wings which in the end exerts a downwards pressure to the floor. saying that the fly doesn't matter is like saying that a small boat floating in a bathtub doesn't increase the weight of the tub.
     
  6. Feb 13, 2007 #5

    ZapperZ

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  7. Feb 14, 2007 #6
    My friend alex refutes this and asks: But what if the fly is flying directly above the air conditioning vent?
     
  8. Feb 14, 2007 #7

    ZapperZ

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    Your "friend" alex should stop making you into his patsy and ask the question himself.

    Zz.
     
  9. Feb 14, 2007 #8
    *making you into his patsy*:rofl: But I like frilly things :cry:
    He cant be flucked to register so I'm just copy'n'pastin his replies from our e-mails at work... I think it would still add to the weight of the plane becasue it's still flying...

    Now if the fly was dead and being suspended in midair by the updraft from the air conditioning vent would it add to the weight then?
     
  10. Feb 14, 2007 #9

    ZapperZ

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    It is bad enough trying to explain things on here to someone directly. It will be worse, as far as communication is concerned, to try and carry a discussion via a 3rd party. I certainly have no patience to carry such a thing.

    Zz.
     
  11. Feb 14, 2007 #10
    Fair enough but this question *If the fly was dead and being suspended in midair by the updraft from the air conditioning vent would it add to the weight then?* was mine :D Unless your stumped...:biggrin:
     
  12. Feb 14, 2007 #11

    ZapperZ

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    1. You will first note that your ORIGINAL question was already answered.

    2. This is now a different question and when you add complexity to the problem, you also must make the question clearer by specifying if you make any assumption about the time of air flow - laminar or turbulent. You also need to specify if you assume that the air flow couples to the rest of the air in the room, i.e. is it a continuous flow, or simply a one-way flow?

    You will notice that in physics, as soon as you try to go beyond the simplest scenario, then the QUESTION itself needs to be clearly presented if you expect any kind of unambiguous answer.

    It is strange that you claim now that this question is "yours", when you said this earlier:

    Zz.
     
    Last edited: Feb 14, 2007
  13. Feb 14, 2007 #12
    Yeeeeea cos he said it was flying... and im saying if it were dead....:uhh:

    OK, heres the evolved form of the question...

    A man flies a small light aircraft straight and level. Inside the cockpit is a dead fly being suspend in midair by the updraft from the aircrafts AC. Does the fly’s weight contribute to the aircraft’s weight at all????
     
  14. Feb 14, 2007 #13

    ZapperZ

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    It doesn't matter if it is suspended by the aircraft AC or by a string. If it is a closed system, then the answer is the same. If it is suspended by the draft coming from OUTSIDE the plane (windows open), then this is different. One can already see that if one removes the airplane - the bird will still be suspended. That is why I asked about how the air was "coupled" to the system, etc.

    NOW do you see what I was getting at? If you only want to reveal only bits and pieces of the question rather than the whole question (something we REQUIRE if this is a homework or schoolwork-type question), then you will get the vague answer commensurate with your vague question.

    Zz.
     
  15. Feb 14, 2007 #14
    :rofl: It's a stupid question that we made up at work to pass time! You really shouldn't be gettin so worked up over something so trivial, it's bad for your heart :uhh:
     
  16. Feb 14, 2007 #15

    ZapperZ

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    We (or I) can't tell when a question is "serious" or "stupid". We treat all questions the same way. Besides, you were trying to ruffle my feathers by insinuating that I was 'stumped', which forced me to point out how ambiguous your question was for a clear answer.

    If you wish to continue participating in this forum, keep that in mind.

    Zz.
     
  17. Feb 14, 2007 #16
    Unless you're stumped... :rofl: It was a joke dude! Are you gonna stop me posting on the forum for having a sense of humor?

    Anyway back to the question... In light of your answer some aspects need to be cleared up...

    Where did you get the ridiculous notion of a bird being suspended when we were talking about a fly? Is it possible on a metaphysical level for a fly to spontaneously transform into a bird? If so could its weight be supported by the air conditioning system?
     
    Last edited: Feb 14, 2007
  18. Feb 14, 2007 #17

    ZapperZ

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    Does it really matter if it is a fly, a bird, a bowling ball, etc, and if it is suspended via floating in air, by a string, or by an air balloon?

    All we care about is (i) if the object is suspended in air (i) by what mechanism and (iii) if this mechanism is part of the system under consideration or not?

    You'll notice that I spent considerable effort whereby I didn't just TELL you the answer, but I spent time trying to explain why it is so.

    And note the POINT I was making when I brought up your statement about me being stumped. It wasn't about your posting, but rather in response to YOUR assertion that I shouldn't be "so worked up". I made no connection between your "joke" and your ability to post on here.

    Zz.
     
  19. Feb 14, 2007 #18
    Oh ok...:yuck:...
    As long as we are both on the same page that this is a TRIVIAL question, I'm not out to make air travel safer or create the next type of fuel...

    Do you feel that you are doing a public service by answering an immensely banal question with the utmost authority and seriousness? It tests me to respect you as an "intellectual" if you cant see the funny side of this...you have a mother!:surprised
     
  20. Feb 14, 2007 #19

    ZapperZ

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    Some of the most profound insights into physics came out of trivial observations! I can give you tons of examples. You'd think that the "physics of ribbon curling" that you'd find in gift packages is utterly trivial. Yet, the physics could have an impact in manufacturing and nanotechnology! So no, any physics question in this forum is not taken to be trivial, unless it is obtuse, vague, and plain silly.

    Furthermore, this IS a physics forum, and you asked a physics question in the physics section of the forum. If you had intended this to be nothing more than a joke, I would have suggested that you post this in the General Discussion forum, not in here, where the posts are more heavily moderated to stick closer to the topic.

    Zz.
     
  21. Feb 14, 2007 #20

    DaveC426913

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    Zapper, he's got you there. You are obviously out-of-touch with the spirit and intent of the Physics Forum - what with your mere 6000+ posts and four year+ attendance. mrcore64 clearly has his hand on the pulse of the PF forum, having been here for several days now. Clearly, he knows why PF members come here every day. :biggrin:



    mrcore64: Seriously dude, you've virtually stepped off the elevator into the office on your first day of work, and by 9:02 you're telling people that you know how the place runs and insulting people.
     
    Last edited: Feb 14, 2007
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