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Need help on a forces and equilibrium question

  1. Feb 7, 2013 #1
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    Its part B that I'm not sure about.

    I know how to do it. But I'm confused about why the support force is not acting vertically upwards (so no horizontal component).

    I assumed that the support force would always be directly perpendicular to the ground/slope/wall.

    Can someone explain this?
     
  2. jcsd
  3. Feb 7, 2013 #2

    SammyS

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    Apparently the lower end of the girder is not free to slide along the ground. Maybe it's digging into the ground or perhaps, it's prevented from sliding to the left by some obstruction.
     
  4. Feb 7, 2013 #3
    does this count as surface friction of the ground, or is it totally different?
     
  5. Feb 7, 2013 #4

    SteamKing

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    It could be friction, it could be some obstruction against which the beam is resting, whatever.
     
  6. Feb 7, 2013 #5
    oh I see then, so the only reason why the support force in this question isn't acting perpendicular is because the ground isn't totally smooth, right?
     
  7. Feb 7, 2013 #6

    SteamKing

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    For the purpose of this problem, yes.
     
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