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Motion of hawks

  1. Apr 9, 2015 #1
    I am in nature,and I am watching hawks motion. I knew it before and saw it live now,that when the hawk see the animal that wants to eat,close its feather to go faster.
    I made a thought,and I would like to tell me if it is correct or anything is missed.

    I think that closing its feather,make air pressure smaller because its area becomes smaller,so its power becomes bigger(F,power = P,pressure * A,area).
    Also because its power becomes bigger,its acceleration becomes bigger too(F = m*a).
    For that reason we have bigger speed. (a = du/dt)

    Is that right?

    Thanks in advance.
  2. jcsd
  3. Apr 9, 2015 #2


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    F is force, not power in that equation. And making A smaller makes F smaller not bigger there.

    They fold their wings to reduce the drag force, which brakes them.
  4. Apr 9, 2015 #3
    I see. So we can suppose that we have two forces: F1 is hawk's force and F2 air's force ?
    And after to suppose that F1 stays the same,but F2 becomes smaller cause pressure of air becomes smaller?

    Am I wrong again or no?
  5. Apr 9, 2015 #4
    Or maybe it is not about pressure,but it is become closing its winger the hawk,the same force as before now pushes the hawk in lesser area.
    So the whole force is lesser? (air resistance with few words)
  6. Apr 9, 2015 #5


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    Yes as I said.
  7. Apr 9, 2015 #6
    I asked a guy also,about air resistance.
    I asked him,why air resistance becomes smaller when we minimize our area,and he answered me that it is about fluid mechanics.
    Also he told me that it is a bit complicated and not so straightforward as in classic mechanic.
    Is that true?
  8. Apr 9, 2015 #7


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    Well, you are jumping into the theory of flight by energy into the deep end first ! :wink:
    It's usually best to start with fixed wing aircraft first and that's hard enough.
    AS with most of Nature, we're dealing with a very complicated form of 'Engineering' with birds. The wing has variable geometry and provides both lift and power. Perhaps it would be a good idea for you to look at a website that deals with basics of flying (this one is long but has loads of ideas in it) And here's another one. Or you could just google around and find something to your taste; there are loads of them
    Last edited by a moderator: May 7, 2017
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