Why Did I Get the Wrong Answer for the Force at Point C?

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SUMMARY

The discussion centers on the calculation of the force at point C in a mechanics problem involving moments about point B. The user initially misidentified an angle as 5 degrees instead of the correct 15 degrees, leading to incorrect assumptions about the force's direction. It was clarified that the force at C has both vertical and horizontal components and is not perpendicular to member BD. Properly summing moments requires recognizing these components to achieve accurate results.

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Homework Statement


Here is the question along with part of the solution. I am online concerned about finding the force at C.

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The Attempt at a Solution


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For my solution I decided I would sum the moments about point B. However I ended up getting the wrong answer for the force at C. Does anyone know why?
 
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You didn't follow the solution manual. You should first check your geometry to see that the angle you denote as 5 degrees is actually 15 degrees. But then if you sum moments about B, C has both vertical and horizontal components, it is not perpendicular to the member.
 
PhanthomJay said:
You didn't follow the solution manual. You should first check your geometry to see that the angle you denote as 5 degrees is actually 15 degrees. But then if you sum moments about B, C has both vertical and horizontal components, it is not perpendicular to the member.

Ah, I reoriented BD so that the angle there is 5 degrees instead of 15 :P. So you are saying force C will not be perpendicular to BD?

I just summed the moments about B using their answers. I converted the forces C and P so that they are perpendicular to the link BD and summed the moments. The moment does not equal to zero. Is this an error?

Here is my work:
brCCN.png
 

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