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Homework Help: Component velocity vector

  1. Dec 17, 2009 #1
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Dec 17, 2009 #2

    Päällikkö

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    Please show your own work.

    Use the Pythagorean theorem, sin2x + cos2x = 1, repeatedly.
     
  4. Dec 17, 2009 #3
    I don't know how to start.

    Yes, I figured that out from (5) but the main thing is I don't know understand as to where pythagoras needs to be used.

    First of all U0 is parallel to x-axis, right? (I image a x-as to the right y axis out of the picture and z up).
     
  5. Dec 17, 2009 #4

    Päällikkö

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    Well, I suppose you could do the problem geometrically, but I just crunched through the algebra.
    cos2a + sin2a sin2b = cos2b + (1 - cos2a) sin2b ...
    Write it out, apply the Pythagorean theorem again, regroup, Pythagorean theorem, etc.

    Hope this helps?
     
  6. Dec 17, 2009 #5
    I understand the equality but its the geometry that gives the problem, I want to know where (5) comes from!
     
  7. Dec 24, 2009 #6
    It suprises me no one was able to help with this, from what I thought was a simple geometry, problem. Anyway I figured out myself. It turns out that you'll have to give the bar a length say L and then express each the length of the sides in alpha and beta.
     
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