A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

chrisplusian

  • one year ago

I need help with geometry/ trig problem.... see attachment please

  • This Question is Closed
  1. chrisplusian
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    1 Attachment
  2. chrisplusian
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Not sure how they are finding "d". All they say is "through trigonometry". I didn't do well on my last test and it wasn't because I didn't know the concepts of this class (statics) it was mainly because I couldn't do things like this so I actually need an explanation if you are able. Thanks in advance

  3. Michele_Laino
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    here we have to apply this vector equation: \[{\mathbf{M = OP \times F}}\] where \(P\) is the application point of force \(F\)

  4. chrisplusian
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I am actually ok with the ideas in this section.... I see what your trying to say, that the cross product of the position vector and the force vector is the moment about the point. I don't have a problem with that. In this problem they want you to use the M=Fd where d is the moment arm. I can't figure out how to dissect the diagram in a way that I can find d. So I am trying to take a step back and understand how they did it. All they said was "the moment arm d in the figure can be found from trigonometry. I am good with trig, but I don't see how they are doing it.

  5. Michele_Laino
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    we can compute such vector, developing the determinant of the subsequent matrix, along the first row: \[\left\| {\begin{array}{*{20}{c}} {{\mathbf{\hat x}}}&{{\mathbf{\hat y}}}&{{\mathbf{\hat z}}} \\ {d\cos 30}&{d\cos 60}&0 \\ {F\cos 45}&{ - F\sin 45}&0 \end{array}} \right\|\] where \(d=3\) and \(F=5\)

  6. Michele_Laino
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    as we can see, only the \(z-\) component is different from zero

  7. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    They are doing two things in the diagram : 1) extend the force vector 2) draw a perpendicular from point O to the force extended force vector; the length of this perpendicular is \(d\).

  8. chrisplusian
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @ganeshie8 my thought was that they give me an angle 75 degrees and it is on a right triangle so the other angle between the 3m pole is 15 degrees. Is it valid to use the law of sines when there is a right triangle? If so I thought I could find d that way. Somehow that is not what I think they did. I tried drawing this out and using simple concepts to find something that helped but I couldn't come up with anything. If you could show me visually how they did this I would greatly appreciate it

  9. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1443888969129:dw|

  10. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1443889094948:dw|

  11. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    it is right triangle, with one angle = 75, hypotenuse = 3 you can find the opposite side, \(d\). no big deal

  12. chrisplusian
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Ok I see it now, I can't beleive that was not obvious. Thank you.

  13. ganeshie8
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 2

    np :)

  14. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.