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What is the wind velocity in km/h and what angle it it north of east?

  1. Sep 13, 2004 #1
    A light plane is headed due south with a speed relative to still air of 200 km/h. After 1 hour, the pilot notices that they have covered only 190 km and their direction is not south but southeast. What is the wind velocity in km/h and what angle it it north of east?
     
  2. jcsd
  3. Sep 13, 2004 #2

    Tide

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    The velocity of the wind is the difference between the actual velocity of the plane and the "intended" velocity of the plane.
     
  4. Sep 13, 2004 #3
    ...

    not really...in the book the intended is 240 km/h but the actual is 180 km and the answer they give is 170 k/h with an angle of 41.5 N of E.
     
  5. Sep 14, 2004 #4

    Tide

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    Remember, velocity is a vector!
     
  6. Sep 14, 2004 #5
    but there's no angles given.
     
  7. Sep 14, 2004 #6

    Tide

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    Due south and southeast sound like angles to me! :-)
     
  8. Sep 14, 2004 #7
    i still dont get it. :confused: angle is 45 degrees?
     
  9. Sep 14, 2004 #8

    Tide

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    LaTex doesn't seem to be working so I'll try this:

    The actual speed of the plane is 190/sqrt(2) km/h so it's actual velocity is (1, -1)*190/sqrt(2).

    The "intended velocity of the plane is (0, -1)*200 km/h.

    The difference between them is the wind velocity:
    (190/sqrt(2), 200 - 190/sqrt(2))

    Now just divide the y component by the x component to find the tangent of the angle you're looking for.

    A drawing might help you see it better.
     
  10. Sep 14, 2004 #9

    HallsofIvy

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    That should be the first thing you do!
     
  11. Sep 14, 2004 #10
    Tide, Does Latex work now? I still don't get the answers that the book got using what you did...
     
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