Statics - beam forces and moments

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Discussion Overview

The discussion revolves around analyzing forces and moments in a statics problem involving beams. Participants are attempting to calculate moments and clarify concepts related to beam mechanics, particularly in the context of a specific section of the beam from points b to h.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses difficulty in calculating the moment in the section from b to h of the beam.
  • Another participant challenges the correctness of the momentum calculation, stating it should range from 0 at the corner to Pb at the wall, suggesting a need for clarity in definitions.
  • A participant mentions achieving a constant momentum of zero at the h section and seeks validation of this result.
  • Some participants propose that if the problem is purely statics, momentum should not be involved, highlighting a potential confusion between "moment" and "momentum."
  • There is a suggestion to replace the vertical beam with a rope, arguing that only vertical forces are present, which raises questions about the relevance of momentum.
  • One participant states that the moment in the horizontal section can be expressed as P(b-x), comparing it to a cantilever beam without the vertical section.

Areas of Agreement / Disagreement

Participants do not appear to reach consensus on the definitions and calculations of momentum and moments, with multiple competing views on the correct approach to the problem remaining unresolved.

Contextual Notes

There is confusion regarding the distinction between "moment" and "momentum," which may affect participants' understanding of the problem. Additionally, assumptions about the system's configuration and the forces involved are not fully articulated.

almoga
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Summary:: I did the first section but I am having a hard time with the second. would like to find the moment in the next section (from b to h)

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I don't think your momentum is right. The momentum in the top beam ranges from 0 at the corner to Pb at the wall, so pb+px can't be right, however you define x. (I don't see it on the drawing)
When analyzing a beam in wall/floor problem, it's usually easiest to start at the end of the beam. The section from h to the end is very simple, so you can also analyze the section from the cut in the top beam to the end at once. There really shouldn't be a problem if you set the total force and the momentum at any point at 0.
 
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you were right about the b section. I corrected it. I ended up with a constant momentum of zero at the h section. does this make sense to you?
 
I think you can replace the vertical beam with a rope. There's only vertical forces, so how could there be a momentum?
 
willem2 said:
I don't think your momentum is right. The momentum in the top beam ranges from 0 at the corner to Pb at the wall
almoga said:
you were right about the b section. I corrected it. I ended up with a constant momentum of zero at the h section
If this is truly a statics problem, there is no momentum involved at all. There seems to be confusion between a "moment" and "momentum." They are quite different matters.
 
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willem2 said:
I think you can replace the vertical beam with a rope. There's only vertical forces, so how could there be a momentum?
You need to balance forces and also moments.
 
The moment in the horizontal section is P(b-x). Basically, this is the same thing as a cantilever beam without the vertical section.
 
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