1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Helicopter flying around a square course

  1. Jan 4, 2017 #1
    1. The problem statement, all variables and given/known data
    helicopter is flying in air it goes A,B,C,D points
    which are distributed in square
    and helicopter goes one circle in 4 hours
    if wind is blowing in direction from A to D
    then the whole circle is flown in 3 hours
    question: how does it takes to fly from A to C if wind blows in the same direction

    2. Relevant equations


    3. The attempt at a solution
    if the whole circle needs four hours without wind then to go one section of square needs 1 hour
    and lets call the length of one section x and the same will be velocity x km/hour
    lets call velocity of wind y
    see the graph in the file attached
     

    Attached Files:

  2. jcsd
  3. Jan 4, 2017 #2

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    It is not clear to me whether the flight path is ABCD (not a circuit, or circle) or ABCDA. From the fact that it takes less time with the wind, it seems it must be just ABCD. If so, it takes 4/3 hours per leg without wind.
    Also, your diagram is wrong. You have drawn it as though the helicopter still flies as though there is no wind and accepts being blown off course. The only adjustment is to switch to flying back to the West before reaching C. My reading of the question is that the helicopter adjusts so as to still visit all four points.
     
  4. Jan 4, 2017 #3

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    If the helicopter is still supposed to reach B and C, that doesn't work.

    With wind it is impossible to make the round-trip A->B->C->D->A in less than four hours.
     
  5. Jan 4, 2017 #4
    the question is to get to c straight from diagonal
    second remark that's why I draw the graph like trapezoid in order to make helicopter fly in 3 hours
     
  6. Jan 4, 2017 #5
    the only available path is at first from a to b then to c then to d and back to a
    and saying it takes 4/3 per leg is wrong four hours is needed to get back to a from a through those other points
    on diagram I think that if fling to say from a to b than it will go to point e not to b
    and I guess that if It still goes to the same points then it would be impossible to get back in 3 hours
     
  7. Jan 4, 2017 #6

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    But why are you so sure it returns to A? Are you sure you are reading the question correctly? I cannot see that allowing it to miss points B and C is an acceptable reading.
     
  8. Jan 4, 2017 #7

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Even with the shortcut, missing B and C, you cannot make a round-trip in 3 hours. The shortest possible trip will be ~3.7 hours.
     
  9. Jan 5, 2017 #8
    can you read Russian ?
    if yes text is in file attached here
    number 1.3 I translated it the way I understood maybe I am wrong
     

    Attached Files:

  10. Jan 5, 2017 #9

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    No, I can't read Russian, so I typed it into an online translator and got this:
    "The helicopter with there is no wind consistently essential items 1 2 3 and 4 and in the corners of the Square (the shortest distance) for 4h. When the wind, contribute positively in the direction of from 1 to 4, the overflight of the same items for the same route as well..."
    (I substituted 1, 2, 3, 4 for A, B, C, D to avoid confusion.)
    Sounds to me like it is only saying it visits the four points. Nothing about its being a cycle, or returning to the start. I'll try another translator.

    Next translator:
    "
    Helicopter with absence of wind consistently flies items 1 2 3 and 4 are situated in the corners of a square (the shortest distance) 4h.

    When the wind blowing in the direction of from 1 to 4, while overflight of the same items on the same route still..."
     
    Last edited: Jan 5, 2017
  11. Jan 5, 2017 #10

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    That still doesn't lead to a solution. If 1->2->3->4 needs 4 hours without wind, with wind it needs at least 3.8 hours.
     
  12. Jan 5, 2017 #11

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    How true. Maybe the 3h and 4h are swapped around. But I still can't see any implication that the route completes the square.
     
  13. Jan 5, 2017 #12

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    If we swap 3 and 4 hours, then both completing the square and not completing it makes a reasonable problem.
     
  14. Jan 5, 2017 #13

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Of course. That's why I mentioned that, even with the times swapped, I don't detect in the translations any implication that the route completes the square.
     
  15. Jan 5, 2017 #14

    ehild

    User Avatar
    Homework Helper
    Gold Member

    "The helicopter flies over corners of a square A, B, C, and D. Without wind, the route takes 4 hours. If wind blows parallel with the direction from A to D, the same route takes 3 hours. How long does it take to fly along the route AC in the same weather? "


    According to my dictionary, the word "obletaet" can mean a route A to B, B to C and C to D, but also a route around all points. In this case, the time can not be shorter than 4 hours in wind.
    It is not sure if route AC means flying directly from A to C, along the diagonal, or it means ABC?
     
    Last edited: Jan 5, 2017
  16. Jan 6, 2017 #15

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Probably ABC, but that is a question for later, when the given information is consistent.

    @giokrutoi: Please help with the translation issues.
     
  17. Jan 6, 2017 #16

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    For the last part, Google translate gives

    How much time will fly by helicopter from AC with the same direction of the wind?

    So I would say the question is unclear.
    @giokrutoi , if you have the book answer, we might be able to reverse engineer the question. Otherwise I suggest abandoning it as incomprehensible.
     
  18. Jan 8, 2017 #17
    answer is 1 hour
     
  19. Jan 8, 2017 #18

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    I tried modelling the following variations:
    ABCD (not returning to A) takes 4h no wind, 3h with wind; or swapping 3h and 4h
    Wind direction is AD; or wind direction is AC

    Results:
    4h no wind, 3h with wind, never yields a feasible solution (so no point in trying returning to A)
    Otherwise:
    Code (Text):

    ABCD      ABCD         wind           AC with
    no wind   with wind    direction      wind
       3          4           AD            0.81
       3          4           AC            0.84
       4         10.2         AD            1
       4         10.2         AC            1
       3          3.0         AD            1
       3          3.1         AC            1
     
    I'm out of ideas.
    Note how insensitive it is to whether the wind is AD or AC.
    Note also the ambiguity that arises when the ABCD time is the same, with or without wind. Two quite different wind speeds can satisfy the conditions.
     
    Last edited: Jan 8, 2017
  20. Jan 9, 2017 #19

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    I don't find a meaningful solution either.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Helicopter flying around a square course
  1. A Helicopter (Replies: 5)

  2. Hovering helicopter (Replies: 6)

  3. Helicopter, velocity (Replies: 3)

Loading...