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Homework Help: Relative Velocity of birds

  1. Sep 24, 2007 #1
    Canadian geese migrate essentially along a north-south direction for well over a thousand kilometers in some cases, traveling at speeds up to about 100 km/h . If one such bird is flying at 100 km/h relative to the air, but there is a 42.0 km/h wind blowing from west to east.

    Part A) At what angle relative to the north-south direction should this bird head so that it will be traveling directly southward relative to the ground?

    I got this part! 24.8 (I don't know if this is needed in the next part, so I thought I would mention it)

    Part B) How long will it take the bird to cover a ground distance of 600 from north to south?

    I tried to do it like the example in the book, using what is basically the pythagorean theorem. The bird travels at 100, wind is 42, leaving a hypotenuse.

    So I did 100^2 + 42^2 = C^2 = 108.4km/h
    Then, to get how long it takes to travel 600km I did 600/108.4 = 5.5 hours.

    It was incorrect. What did I do wrong?
  2. jcsd
  3. Sep 24, 2007 #2


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    The answer to A) is right.
    The approach in B) seems right as well, only you didn't apply the Pythagorean theorem correctly. Draw the triangle on a piece of paper... what are the straight sides and what is the hypotenuse? Then fill in the numbers and solve for the side you need.
  4. Sep 24, 2007 #3
    Thank you! I completely missed that.

    I hope you guys can count the time you spend here as volunteer experience, everyone is so helpful!
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