# Determining the magnitude of the projected component of the force problem [closed]

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. • Can you show us your calculation? – Superfast Jellyfish Feb 5 '20 at 4:22
• 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. – Albert Goldman Feb 5 '20 at 4:25
• Oh, you just add them. I understand now. – Albert Goldman Feb 5 '20 at 4:40
• Yes. Because it is a scalar. – Superfast Jellyfish Feb 5 '20 at 5:40