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Homework Help: Force projection onto body's axis

  1. Sep 20, 2010 #1
    Hey PhysicsForums. Long time reader looking for some assistance

    1. The problem statement, all variables and given/known data

    [PLAIN]http://img205.imageshack.us/img205/3923/physicsg.jpg [Broken]

    2. The attempt at a solution

    I'm pretty sure the idea is to find the unit position vector to point A, and the force vector F.

    I found the unit position vector to be u = (-4/6)i +(4/6)j + (2/6)k, and the force to be F = (560cos60sin30)i + (560cos60cos30)j + (560sin60)k

    Dotting them together gives me 230 lb, but Mastering Engineering doesn't agree with me. Can anyone point out where I went awry?

    Thanks for reading!
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 20, 2010 #2


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    The x-component of F should be negative. The rest looks fine to me.
  4. Sep 20, 2010 #3
    Simple mistakes are embarassing :(

    Thank you for your careful eyes!
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