Statics - Finding Tension

  • #1

Homework Statement




35197w2.jpg

Homework Equations



The answer in the back on the book shows 4.06i -7.61j + 5.07k. I do not understand why my signs are backwards.


The Attempt at a Solution



w1uwlv.jpg


I ended with -4.06i +7.61j - 5.07k
 

Answers and Replies

  • #2
gneill
Mentor
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The tension involved is a vector that points from B towards A. You've created a vector rab that points from A to B.
 
  • #3
ok thank you. Since i did not see an arrow i was not sure which direction to pick. How did you tell?
 
  • #4
gneill
Mentor
20,922
2,866
ok thank you. Since i did not see an arrow i was not sure which direction to pick. How did you tell?
It's difficult to push with a cable :)
 
  • #5
The tension involved is a vector that points from B towards A. You've created a vector rab that points from A to B.

It's difficult to push with a cable :)


That is a good point. Thank you
 
  • #6
3
0
That is a good point. Thank you

Additionally, there is a weight pulling the boom downwards (or in the negative z-direction). In order to counteract this, the cable needs to pull it upwards (positive z-direction).
 

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