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Determine magnitude of the components of these forces

  1. Jan 12, 2008 #1

    pka

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    1. The problem statement, all variables and given/known data
    Resolve the force F2 into components acting along the u and v axes and determine the magnitudes of the components.

    So! I was able to finally determine F2u. I cannot for the live of me get F2v. I am having a very hard time solving this problem. I have included the diagram of the problem. All of it is what is given.

    Here is the link to the image:
    http://i16.tinypic.com/6je9m60.jpg


    Alright! So in order to first solve for F2v I constructed a triangle where the left side was the F2 force of 500 N and the right side was the F2v vector. They're both connected by the same point. It looks exactly as in the diagram I included. And via the diagram included I determined that the angles inside the triangle are 45, 65 and 70 counterclockwise. So! I used the Law of Sines. F2v is then 482 N.

    Ok, so in order to calculate F2u I tried something similar but my numbers are far too large. I get numbers in the range of 600-1000 N. And...F2v should be 376 N. I tried the same thing I did with F2v but I can't seem to determine the base angles so that I can use Law of Sines again. I get 115 degrees as the angle between the concurrent forces (F2 and F2u). But I don't know how to get the other two angles. I'm just stumped. I thought maybe a different approach would be better. So I tried just solving for the opposite side of the u line to get F2u...In other words I said that F2u is (500 N)*cos(65 deg). 65 because that's the angle between 70 and 45. And...well I get 211 N. But that's not it either. =/

    If anyone could tell me the way I'm supposed to be thinking about this problem I would greatly appreciate it because there are more problems like there I'm having trouble with but I really need some help. hahaha. Many thanks in advance!

    --pka
     
  2. jcsd
  3. Jan 12, 2008 #2

    hage567

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    Homework Helper

    You mean you can't get F2u? You just said that F2v was 482 N and then you said it was 376 N. I'm not sure I'm following...

    Where you are taking your F2u? It should be from the tip of F2v (so along the v axis) to the tip of F2 and it will be parallel to the u axis. Those angles you stated are correct for the triangle those vectors form. You should just be able to use the sine law to get the answer.
     
    Last edited: Jan 12, 2008
  4. Jan 12, 2008 #3

    pka

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    OOOOOHHHH! Thank you so much. I hadn't realized that the triangle I constructed was parallel to u. And yes, it was F2u is the one I needed to find. And of course it parallel right? Because otherwise how could I possibly have determined the angles of the triangle. I made this problem more difficult for myself than it needed to be. lol. In any case, thank you for the help!
     
  5. Jan 12, 2008 #4

    hage567

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    You're welcome.
     
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