Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Will there be a rotation around z axis?

Tags:
  1. Oct 21, 2015 #1
    IMG-20151021-WA0003.jpeg Hello people,

    I know it seems like a silly question. In case 1, its clear that no rotation will occur around z axis. Anyhow, case number 2 is confusing me; I cant decide clearly if a rotation will occur since a moment should be generated around z axis, but in the same time, the line of the acting force is perpendicular on the pivot !

    what do you think please, will it rotate in case 2 ?
     
    Last edited: Oct 21, 2015
  2. jcsd
  3. Oct 21, 2015 #2

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hello Peter, welcome to PF :smile: !

    So what are these ? flexible water hoses or stiff metal rods ?
    A bit of description would really help clear this up !
    What is the criterion to decide whether or not somethign will rotate arountd the z-axis ?
     
  4. Oct 21, 2015 #3
    Hello,
    Cheers :)

    --------------
    any of the two structures consists of beams.

    The structure looks like the English letter "L", where in the second case, the beam in y axis has a bucking,

    in the second case, rotation means that the beam in Y axis, which is in XY plan, will rotate to the x axis.

    :)
     
  5. Oct 21, 2015 #4

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    So what is the full problem statement ?
    Why are those pivot points marked ?
    Is there any support point somewhere ?
    The F indicate loads along the y axis ?
    What is the criterion to decide whether or not something will rotate around the z-axis ?
     
  6. Oct 21, 2015 #5
    ok,

    I will upload another drawing for case 2> to be clearer :)
     
    Last edited: Oct 21, 2015
  7. Oct 21, 2015 #6

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    no spports ? not even or the pivot points ?

    And in case 1 everything is in the yz plane ?
    And in case 2 everything is in the yz plane ?

    the full problem statement ?
     
  8. Oct 22, 2015 #7
    Hello,

    Kindly, find this sketch.

    the statement is about to answer whether the curved beam will rotate around z axis or not, at the current position, and from the steady state status, due to the applied load>
     

    Attached Files:

    • kk.jpg
      kk.jpg
      File size:
      34 KB
      Views:
      69
  9. Oct 22, 2015 #8

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I would call this case 3, to me it looks different from the others

    I take it the left-handed coordinate system is accidental -- the axis that's pointing to the right is the z axis ( -- although 'z' ?)

    And I assume the 'triangle' beam - beam - curved beam can only rotate around this z-axis, and that the arc with two arrows is in the xy plane.

    The perpendicular distance from the line of action is zero: the line of action goes through the candidate rotation axis.
    So the torque is zero and no rotation will occur.

    But it's an unstable equilbrium ...
     
  10. Oct 22, 2015 #9
    Hi,

    yes, its corresponding assumptions.

    The thing which is confusing me, that this load will be analysed like in the photo, and thus a torque should be generated..

    So, is there any physical way that can help to overcome this anomaly position ?
     

    Attached Files:

    • kkk.jpg
      kkk.jpg
      File size:
      31.3 KB
      Views:
      62
    Last edited: Oct 22, 2015
  11. Oct 22, 2015 #10

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    by whim ?

    If ##\vec F## is in the yz-plane, there can't be a net component pointing outside that plane. Your sketch suggests ##F_z## in the yz-plane and ##F_1## along the curvature or something ?
     
  12. Oct 22, 2015 #11
    sorry im not good in drawing :)

    Is there is any way to to overcome this anomaly situation, so we can make the curved beam rotates. I said that in the meaning of modifying the curved beam design somehow in order to divert the direction of the applied force and then to create a torque that able to create rotation ?
     
    Last edited: Oct 22, 2015
  13. Oct 22, 2015 #12

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    • So far we've ignored the weight of the curved beam. That alone will make it rotate anti-clockwise.
    • Even if the curved beam has weight 0, it still is an unstable equilibrium, so in reality it will rotate, either clockwise or anti-clockwise.
     
  14. Oct 22, 2015 #13
    So, this may happen while the exerted force is existing in this position. right ? :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Will there be a rotation around z axis?
Loading...