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I can't figure out this homeworm problem. I know the answer is 147 N, but I don't know why.

Determine the magnitude of the projected component of the force F = { 450 i - 250 j + 650 k } N acting along the cable CA.

I found the unit vector, found the dot product of the force and the unit vetor, and found the magnitude. I got 491 N, which is way off the mark. Is it because it's CA instead of AC? I don't think that would effect magnitude though.

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  • $\begingroup$ Can you show us your calculation? $\endgroup$ – Superfast Jellyfish Feb 5 at 4:22
  • $\begingroup$ sqrt(36 + 1 + 9) = 6.8. unit vector = (-6,1,3)/6.8 = (.8824,.14706,.44118). 450 * .8824 i + -250 * .14706 j + .44118 * 650 k. I then squared all of the components added them, and found the square root of that. Sorry, I don't know mathjax. $\endgroup$ – Albert Goldman Feb 5 at 4:25
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    $\begingroup$ Oh, you just add them. I understand now. $\endgroup$ – Albert Goldman Feb 5 at 4:40
  • $\begingroup$ Yes. Because it is a scalar. $\endgroup$ – Superfast Jellyfish Feb 5 at 5:40