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Tension in cable and reaction force

  • Thread starter Woopydalan
  • Start date
  • #1
744
2

Homework Statement





Homework Equations





The Attempt at a Solution


For this problem, what I am confused about is the fact that the Z direction parts of the tension will tend to rotate in a direction different from the Y components of the tension and the 850 lb vertical force. I am not sure how to reconcile the moments involving the Z-component into my moment equation around point A, which I know should be zero. The x component is along the line of point A, so there moments must be zero.

I remember solving 2-D moments and the x components and y components will cause rotation in the same direction, but with 3-D moments it appears the z component will rotate around a different direction than the y component will, so it seems unlikely that they can be added together like the x and y components can be in 2-D torques.

I know the page is cut off, but I don't get the right value when I do it this way. I know the part about the forces is correct, there is something that I am missing though with respect to taking a moment around point A, which I want to do in order to get rid of the reaction forces at A.
 

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Answers and Replies

  • #2
44
1
Taking a moment with respect to point B should give you more simple equations.

If you are doing scalar analysis, you should break your moment into Mx, My, Mz. Use M = r x F instead for vector analysis.
 
  • #3
744
2
Thanks, I took the moment at point B and got it solved
 

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