Force projection onto body's axis

  • Thread starter Bismuth
  • Start date
  • #1
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Hey PhysicsForums. Long time reader looking for some assistance

Homework Statement



[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!
 
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Answers and Replies

  • #2
vela
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The x-component of F should be negative. The rest looks fine to me.
 
  • #3
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Simple mistakes are embarassing :(

Thank you for your careful eyes!
 

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