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brinethery

Anyone good with vector problems involving moments?

  • 2 years ago
  • 2 years ago

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  1. brinethery
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    Is my method correct or was I reading the problem wrong?

    • 2 years ago
  2. brinethery
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    http://www.scribd.com/doc/86313887/Problem-6

    • 2 years ago
  3. eashmore
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    I don't understand what they mean by "equally inclined to the positive ends of the orthogonal axis," but your methodology looks correct and complete.

    • 2 years ago
  4. No-data
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    You're totally wrong.... sorry

    • 2 years ago
  5. No-data
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    Just kidding. Your method is correct and you get the right answer. Congratulations.

    • 2 years ago
  6. brinethery
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    @eashmore my instructor writes all of these problems and this was the practice final exam. I think he wanted to make the questions as hard as possible. He wanted us to work backwards (r crossed with F = moment, so find the components of F). Equally inclined means this: You have an angle with the x-axis, with the y-axis and the z-axis. (Sorry if this info is nothing new to you!). A vector in 3-space has those 3 direction angles: alpha, beta, and gamma. If all angles are equally inclined, you can say: alpha=beta=gamma = theta (we'll just use theta so as not to cause confusion). If you square the cosine of each angle, that will equal 1. cos^2(alpha) +cos^2(beta) +cos^2(gamma) = 1 Since the angles equal eachother (equally inclined with the positive axes, we can say: cos^2(theta) +cos^2(theta) +cos^2(theta) = 1 3 cos^2(theta) =1 cos^2(theta) = 1/3 cos (theta) = 1/sqrt(3) Therefore, all alpha, beta, and gamma have direction cosines of 1/sqrt(3) So after all of that work, your unit vector will be: (1/sqrt(3))i +(1/sqrt(3))j +(1/sqrt(3))k Pg. 29 seems to explain this concept fairly well (see attached).

    • 2 years ago
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  7. No-data
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    I can give you harder problems if you want to practice.

    • 2 years ago
  8. brinethery
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    Well it was just the wording. Sometimes I have to read the question a few times to figure out what he wants.

    • 2 years ago
  9. brinethery
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    To be fair, some other people were on here last night and had no clue what was going on. Well I finished my final today and I'm all "vectored" out.

    • 2 years ago
  10. No-data
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    Yeah that equally inclined thing it's weird. Haha I bet you'll get a good grade.

    • 2 years ago
  11. brinethery
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    I will tell you what I don't get. The instructor gave 2 hours for the test. Some people finished in 50min, got up and left. Why not just sit around for the whole 2 hrs?

    • 2 years ago
  12. No-data
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    Well noboyd would notice them if they stay sit.

    • 2 years ago
  13. No-data
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    Or maybe they had to go to the bathroom =P

    • 2 years ago
  14. brinethery
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    HAHAHAHAHA I have something funny to mention

    • 2 years ago
  15. brinethery
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    I took multivar. calc last quarter and my teacher had us take the exams in the testing center. My classmate would sit in the testing center for like 5 hours taking her test. I asked her how she resisted going to the bathroom. She's like... I just hold it in.

    • 2 years ago
  16. No-data
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    Ohh poor girl! Five hours is insane!

    • 2 years ago
  17. brinethery
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    My instructor was really tough. The exams were all application-based and it had been 5 years since I'd been into math. My dad convinced me to sign up lol.

    • 2 years ago
  18. No-data
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    I wish you could help me with multivar calc. later

    • 2 years ago
  19. No-data
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    I don't quite understand. In which grade are you?

    • 2 years ago
  20. brinethery
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    I changed my mind about what field I want to go into.

    • 2 years ago
  21. brinethery
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    I took 3 quarters of calc starting when I was 17 and I'm 24 now.

    • 2 years ago
  22. brinethery
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    Which grade am I in? "Starting over!"

    • 2 years ago
  23. No-data
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    Sorry, but what were you studying before?

    • 2 years ago
  24. brinethery
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    to get into pharmacy school

    • 2 years ago
  25. No-data
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    Did you want to be a mathematiciand and then changed your mind?

    • 2 years ago
  26. brinethery
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    Nope, I am retarded at math compared to other people.

    • 2 years ago
  27. No-data
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    and now what is your major? Engineering?

    • 2 years ago
  28. No-data
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    I know you're not retarded but I can say is useful to think that haha.

    • 2 years ago
  29. brinethery
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    I think civil would be a good path. And hopefully I could get a job with county... anything having to do with infrastructure.

    • 2 years ago
  30. No-data
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    Ahh yeah! I remember you told me that long time ago!

    • 2 years ago
  31. brinethery
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    It's okay.

    • 2 years ago
  32. No-data
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    If I had to build a house I would call you =P

    • 2 years ago
  33. brinethery
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    It would crumble LOL!!!!!

    • 2 years ago
  34. brinethery
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    Hahaha "structurally unsound"

    • 2 years ago
  35. No-data
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    I'm so used to that now.

    • 2 years ago
  36. No-data
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    Do you study there ATM?

    • 2 years ago
  37. No-data
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    Please tell me when you get into statics. I have plenty of doubts on that!

    • 2 years ago
  38. brinethery
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    I'll brb... sec

    • 2 years ago
  39. eashmore
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    Thanks for the explaination of 'equally inclined.' @brinethery I've never heard that expression. Civil is a great field if you're interested in infrastructure. Everything from sky-scrapers to drainage ditches! Keep up the great work! You're problems are always challenging and then you end up solving them before I can!

    • 2 years ago
  40. brinethery
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    My teacher responded to my email this morning after I sent him the pdf file of what I wrote. He's like... no, no! Here's how you do it! Again, Jae saves the day :-)

    • 2 years ago
  41. No-data
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    what pdf?

    • 2 years ago
  42. No-data
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    Who is Jae?

    • 2 years ago
  43. brinethery
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    My instructor.

    • 2 years ago
  44. No-data
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    Was your problem wrong?

    • 2 years ago
  45. brinethery
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    You know the program Adobe that opens up those document files where you can only view them and do a tiny bit of editing? That's a pdf file.

    • 2 years ago
  46. No-data
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    hahaha I know what a pdf is =P

    • 2 years ago
  47. brinethery
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    The original problem was wrong. But then I uploaded the revision to Scribd. The link remains the same if it's a revision.

    • 2 years ago
  48. No-data
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    I meant what was the content of the pdf?

    • 2 years ago
  49. No-data
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    ahhh!

    • 2 years ago
  50. brinethery
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    I think I trashed the original, but it's wrong lol. But the current version is correct. I thought he was saying that F sub x and F sub y were equally inclined. But he corrected me on that.

    • 2 years ago
  51. No-data
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    That is great! I wish I had teachers like him =P

    • 2 years ago
  52. No-data
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    I had one but I failed miserably in his class. Shame on me.

    • 2 years ago
  53. brinethery
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    Actually he's teaching engr 106, but another instructor writes all of the exams and final exam. So that's probably why the exams are worded so strangely.

    • 2 years ago
  54. No-data
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    Thank you. I'd apreciated that!

    • 2 years ago
  55. brinethery
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    k, I'll create a link.

    • 2 years ago
  56. No-data
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    I want so bad to understand Maxwell's equations, but I suck at Calculus hehe

    • 2 years ago
  57. No-data
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    Perfecto!

    • 2 years ago
  58. brinethery
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    Sucks, I wish I had all the solns for at least one textbook. I don't think of it as cheating if I'm reading solutions as though I would read a textbook. It just helps to better understand things.

    • 2 years ago
  59. No-data
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    Maybe you're a different kind of learner.

    • 2 years ago
  60. brinethery
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    Sorry @eashmore we can bring the convo outside of here if you keep getting pop-up messages.

    • 2 years ago
  61. eashmore
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    Doesn't bother me. The wealth of notifications strokes my ego a bit. :-)

    • 2 years ago
  62. brinethery
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    Hahaha I'm totally abusing the system :-). I'll try to bring it away from here.

    • 2 years ago
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is replying to Can someone tell me what button the professor is hitting...

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