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Homework Help: Engineering Mechanics Couple system question

  1. May 26, 2005 #1
    what is this problem searching for?

    A 25-lb force acting in a vertical plane parallel to the yz plane is applied to the 8-in.-long horizontal handle AB of a socket wrench. Replace the force with an equivalent force-couple system at the origin O of the coordinate system.

    See attached pic of the problem.

    AO is 15-in.-long vertical

    AB is 30 degrees off the x-axis

    Force(in red) is 25-lb and is 20 degrees from the -z-axis


    ok tell me if I"m wrong.

    I think this problem is looking for the force that should be applied to cancel the other force but still have the same moment about O.

    Please tell me if I'm thinking correctly...

    however, how should I go about doing that? if that is the solution to this problem.

    Attached Files:

    Last edited: May 26, 2005
  2. jcsd
  3. May 27, 2005 #2


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    Science Advisor

    Not exactly. What you need to do is come up with a force and moment that, when applied at the point O, are equivilent to the lone force acting at the end of the handle.
  4. May 27, 2005 #3
    ok, I think I get it.....please correct me if I'm wrong (and let me know if I'm right)...

    First I add vectors that are equal to F and -F at point O.

    then I find the couple produced by F (original force) and -F. That will give me the answer of the couple moment at point O. and then I have F applied at O left over.

    Is that what it is looking for?

    I calculated the following answers:

    M = 196.94i + 352.35j - 128.25k

    F = -8.55j + 23.49k
    Last edited: May 27, 2005
  5. May 27, 2005 #4


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    Homework Helper

    Taiki, you only need to calculate the moment of F with respect to the origin, and put the rectangular representation of F. That should give you your Force-couple system at O.
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