physics- TEST TMRW PLS HELP!

w w w . m e d i a . c h e g g c d n . c o m / m e d i a / a c 3 / a c 3 b b 1 e 1 - 5 b a 8 - 4 1 9 e - 9 a 8 4 -a d 5 0 e 4 6 a 2 9 4 e / p h p s U O o L 3 .p n g

(delete all spaces for link to work)

Determine the magnitude of the resultant moment produced by the forces about point O.

pls explain to me how to do it, you don't need to tell me final answer, i can number crunch :)

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asked by Anya
  1. In general The moment vector about any point O of force vector F is
    M = R x F
    where R is the vector from point O to a (any) point on vector F and F is the force vector

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    posted by Damon
  2. To set this up:
    if R = Rx i + Ry j + Rz k
    and F = Fx i + Fy j + Fz z

    then the vector M is the determinant of the matrix

    | i j k |
    |Rx Ry Rz |
    |Fx Fy Fz)|

    or in other words
    (RyFz-RzFy)i + RzFx-RxFz)j + (RxFy-RyFx)k

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    posted by Damon
  3. Your link did not work for me beyond:
    www.media.cheggcdn.com/media/ac3

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    posted by Damon
  4. there are basically two forces acting on the object.
    so do i find the resultant force first and then cross that with r?

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    posted by Anya
  5. No, find the Moment due to each.
    M1x, M2x
    M1 y, M2y
    M1z, M2 z

    THEN add the moment vector components
    Mtotal x i + Mtotaly j + Mtotalz K

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    posted by Damon

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