1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

3D statics

  1. Jun 28, 2011 #1

    Femme_physics

    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data

    http://img84.imageshack.us/img84/1715/given2.jpg [Broken]

    A weightless beam AO is held in a horizontal position (at the xy plane) as described. At its tip O the ball is attached to a ball joint, and at points C and A its tied via wires. horizontal wire CD and slanted wire AB, whose in the plane parallel to xz. At point E acts on the beam vertical force Q. The shape OKAD is a rectangle (look at the upper view in the drawing).

    Given:


    http://img35.imageshack.us/img35/9106/given1.jpg [Broken]


    3. The attempt at a solution

    http://img215.imageshack.us/img215/2376/per1v.jpg [Broken]

    http://img845.imageshack.us/img845/9779/per2.jpg [Broken]

    They give out Oz as 0.86666 [kN]. I doubt this could just be a rounding error?
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Jun 28, 2011 #2

    I like Serena

    User Avatar
    Homework Helper

    Hey, I recognize this problem! :smile:

    I agree, but I get 0.9 kN as well....
     
  4. Jun 29, 2011 #3

    Femme_physics

    User Avatar
    Gold Member

    Last edited by a moderator: May 5, 2017
  5. Jun 29, 2011 #4

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    It looks like you got the components of TCD switched in your moment equation.

    Hint: You can calculate the moment about O due to TCD more simply since you know the angle between the lever arm and the force.
     
  6. Jun 29, 2011 #5

    Femme_physics

    User Avatar
    Gold Member

    Did I really? What is the angle from Tcd to the Y axis? It's 60! I reckon I got it right.

    Look, I made it more clearly on powerpoint so you'll see exactly what I'm seeing

    http://img11.imageshack.us/img11/7708/metersandeverything.jpg [Broken]

    According to the axes, I used the right distances and angles


    but I don't have to use the diagonal distance.
     
    Last edited by a moderator: May 5, 2017
  7. Jun 29, 2011 #6

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Yeah, I think you are right. It's just a calculation error then. I haven't been able to reproduce your answer from your equation. I get [itex]T_{CD}=\sqrt{3}~\mathrm{kN}[/itex].
    I have no idea what you mean. The torque τ is just τ = rF sin θ = (0.6 m)TCD sin 60.
     
  8. Jun 29, 2011 #7

    Femme_physics

    User Avatar
    Gold Member

    Thanks :smile: I "think" I solved it. I'll post my full solution this evening scanned. Only Oz is different. I noticed the solution manual makes it out to be 1.5 kN, whereas it really should be 0.9 kN
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: 3D statics
  1. 3D statics (Replies: 12)

  2. 3D statics (Replies: 7)

  3. 3D Statics? (Replies: 4)

  4. 3d statics problem (Replies: 2)

  5. 3D statics problem (Replies: 5)

Loading...