Weird question, with strength of materials (probably)

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Discussion Overview

The discussion revolves around a mechanical engineering homework problem related to the Section Modulus, specifically the expression Z = h^2/3. Participants explore the context and calculations involved in determining the Section Modulus for a configuration of vertical parallel bars.

Discussion Character

  • Homework-related
  • Technical explanation

Main Points Raised

  • One participant expresses confusion about the subject matter and seeks clarification on the term "Zb=h^2/3."
  • Another participant suggests that the problem involves two vertical parallel bars of unit width and height h, separated by a distance b.
  • A participant explains that the Section Modulus (denoted as S or Z) is calculated as the moment of inertia of the bars about the center of gravity divided by the vertical distance from the center of gravity to the top of the bars.
  • The calculation provided indicates that the moment of inertia for two bars is h^3/6, leading to the conclusion that S equals h^2/3.
  • There is a note of uncertainty in the calculations, with one participant stating they are "just guessing."
  • A later reply acknowledges the correctness of the previous explanation while expressing surprise at their own lack of awareness of the topic as a Mechanical Engineer.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the clarity of the problem or the student's understanding, with some expressing doubt about the student's capability in the subject matter.

Contextual Notes

There is an implicit assumption about the familiarity with the concepts of Section Modulus and moment of inertia, which may not be shared by all participants. The discussion does not resolve the potential confusion surrounding the original problem statement.

berdan
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Hi,
So,I'm helping a guy with his mechanical engineering homework.
The problem is that the guy is so off, he doesn't even know the name of the subject.
And honestly, I having a hard question finding out what this question is about.
I need to proove the Zb=h^2/3 thingy. I have no idea what this is about.

Can someone point me to the subject?
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it is just a rectangle.
 
Sort of a funky sketch, but I would say what you have here is 2 vertical parallel lines (bars) of unit width and height h, separated by a distance b, and you are looking for the Section Modulus of those parallel bars about the x-axis passing through its center of gravity. Section Modulus is commonly denoted as S (or sometimes Z) where S is equal to the moment of inertia of the bars about the cg and x-axis divided by the vertical distance from the cg to the top of the bars. In which case from tables I is h^3/12 for each bar, twice that for 2 bars, h^3/6. Thus S is h^3/6 divided by h/2, or h^2/3. I’m just guessing though, and in any case it won’t be of much help to him if the whole course is way beyond him, and he should probably choose another career perhaps or get his act in gear.
 
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PhanthomJay said:
Sort of a funky sketch, but I would say what you have here is 2 vertical parallel lines (bars) of unit width and height h, separated by a distance b, and you are looking for the Section Modulus of those parallel bars about the x-axis passing through its center of gravity. Section Modulus is commonly denoted as S (or sometimes Z) where S is equal to the moment of inertia of the bars about the cg and x-axis divided by the vertical distance from the cg to the top of the bars. In which case from tables I is h^3/12 for each bar, twice that for 2 bars, h^3/6. Thus S is h^3/6 divided by h/2, or h^2/3. I’m just guessing though, and in any case it won’t be of much help to him if the whole course is way beyond him, and he should probably choose another career perhaps or get his act in gear.

You are absolutely right in all accounts. Funny thing is that I wasn't aware of this as well, being a Mechanical Engineer with a diploma hah.
Thanks a lot!
 

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