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Homework Help: Statics -- Net Moment

  1. Dec 14, 2016 #1
    1. The problem statement, all variables and given/known data statiics.PNG

    2. Relevant equations
    I can see how the net force is not the same but I'm not getting the net moment.

    3. The attempt at a solution
    12mm x 10N = 120N-mm. How do these two FBDs not have the same net moments.

    Thanks for any help!
  2. jcsd
  3. Dec 14, 2016 #2


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    Staff: Mentor

    Welcome to the PF. :smile:

    What is the actual problem statement? Something about showing the two situations do not have the same net forces and net moments?
  4. Dec 14, 2016 #3
    If I'm reading this right, it looks like the FBD on the right is just the FBD on the left, except it's showing you the moment caused by the 10N force. Or in other words, the 10N force is still there they're just not showing it and the net moment is the same on both. Of course I'm not sure what the actual problem statement is, so...
  5. Dec 15, 2016 #4


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    Science Advisor
    Homework Helper
    Gold Member

    In general, moment depends on the chosen axis. If you choose the left hand end of the bar as the axis then the moments will be the same, but maybe not for other choices.
  6. Dec 16, 2016 #5
    I think haruspex may be correct. They are two separate FBD and the answer to the question is that neither their net force or moment are the same. I may need to over this again.

    If no new comments are posted, thanks for your time!
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