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Homework Help: Last question on vectors.

  1. Dec 2, 2007 #1
    1. The problem statement, all variables and given/known data
    A pilot wants to fly directly to the west. The engine pushes the plane at 100 m/s, and there is a crosswind blowing to the south at 30 m/s. Determine the exact angle at which the pilot should head.

    2. Relevant equations

    3. The attempt at a solution
    Here's what I did:

    100^2+30^2= 10900

    I then did SqRT of 10900 and got 104

    then I did tan negative 1 to find the angle and got 89 degreess

  2. jcsd
  3. Dec 2, 2007 #2
    Hmm, I got 287 degrees. Check your work again.
  4. Dec 2, 2007 #3
    my work shows how I got 89

    how did you get your answer?
  5. Dec 2, 2007 #4
    Well I did it using vectors and then by using a "whiz wheel" and both answers came out the same. You got 104 which is correct, but you can't just take the tan-1 of that. You have to take tan-1 of .3 because 30/100 = .3. That gives you 17 degrees but now if you are heading west and the wind is out of the north you have to point the aircraft into the wind to crab, so you will still track on a westerly heading. Therefore 270 + 17 = 287 degrees.
  6. Dec 2, 2007 #5
    why 30/100 and not 30/100000, 30/89, 30/76, get what I am saying?
  7. Dec 2, 2007 #6
    Simple trigonometry..

    Opposite side = 30
    Adjacent side = 100

    Tan theta = opp divided by adjacent

    To find the angle, you'd take the tangent inverse of it.

    Tan-1 = 30/100

    Which produces 17
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