Engineering Statics Equilibrium System Question

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Discussion Overview

The discussion revolves around a homework problem related to engineering statics, specifically focusing on an equilibrium system involving forces and moments. Participants are analyzing a free body diagram (FBD) and attempting to derive equations for equilibrium.

Discussion Character

  • Homework-related, Mathematical reasoning

Main Points Raised

  • One participant describes their approach to the problem, including drawing a free body diagram and writing equilibrium equations for vertical forces and moments.
  • The participant expresses uncertainty about their solution, suggesting they may have made an error in their calculations.
  • Another participant questions the reasoning behind the initial doubt about the correctness of the answer.
  • A different participant raises the possibility that changing the weight (W) could affect the angle (θ), indicating a relationship between these variables.
  • Concerns are noted regarding the absence of W in the final expression, which could lead to issues with unit consistency.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correctness of the solution, and there is ongoing uncertainty regarding the implications of the weight on the angle and the overall solution.

Contextual Notes

There are unresolved assumptions regarding the definitions of variables and the relationship between W, θ, and other parameters in the problem. The discussion does not clarify the mathematical steps leading to the final expression.

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Homework Statement


http://i.imgur.com/VFb5rwj.png


Homework Equations





The Attempt at a Solution


First, I drew the FBD for the system, one horizontal force at A, one force perpendicular to the beam at B, and the weight.
Writing out the equilibrium equations:
The sum of forces in the y direction should be 0, so I have the equation:
Nb cos(θ) - W = 0, which can be rearranged for Nb later on.
Then I took the moment about point A:
Nb (a/cosθ) - Wcosθ (L/2) = 0
Eventually, it simplifies out to cos^-1 ( (2a/L) ^(1/3) ) = θ

I don't think I got the right answer, but can someone help me identify my error? Thank you in advance.
 
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Why do you think you have the wrong answer?
 
IDK, it looks just so completely wrong. and also it says that describe it in terms of w, a, and l and I have no w.
 
Would changing W also change θ?

Also your answer is consistent with the units. If W was in the solution then the units would get screwed up.
 
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Hmm, I suppose you're right, thank you for the replies.
 

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