Understanding Truss Forces and Solving Equations for Homework Assignments

  • Thread starter Thread starter chetzread
  • Start date Start date
  • Tags Tags
    Forces Truss
Click For Summary

Discussion Overview

The discussion revolves around understanding a specific equation related to truss forces, particularly the expression 8/BD = x/EB, in the context of a homework assignment. Participants express confusion regarding the absence of a point E in the provided diagrams and the lack of dimensions necessary for solving the problem.

Discussion Character

  • Homework-related
  • Debate/contested

Main Points Raised

  • Some participants express confusion about the equation 8/BD = x/EB, noting that point E is not present in the diagrams provided.
  • Several participants question the completeness of the problem statement due to missing dimensions and suggest that the absence of this information makes the problem unsolvable.
  • One participant speculates that the calculation might involve geometry to find an unknown length and suggests that E could be a typo.
  • Another participant argues that dimensions are not necessary for a statically determinate frame, proposing that the proportions alone might suffice for solving the problem.
  • Concerns are raised about the correctness of the suggested external reactions, with a participant indicating that incorrect external reactions would hinder the ability to find internal forces.

Areas of Agreement / Disagreement

Participants generally agree that the problem statement is incomplete and that the absence of necessary information complicates the discussion. However, there are differing views on whether dimensions are essential for solving the problem, leading to unresolved disagreements about the approach to take.

Contextual Notes

The discussion highlights limitations related to missing assumptions and the dependence on the completeness of the problem statement. The lack of clarity regarding the geometry of the truss and the specific roles of points in the diagrams are also noted.

chetzread
Messages
798
Reaction score
1

Homework Statement


i don't understand the 8/BD = x/EB
Can anyone explain about it? There's no point E in the diagram...

Homework Equations

The Attempt at a Solution

 

Attachments

  • 270.jpg
    270.jpg
    19.6 KB · Views: 461
  • 271.jpg
    271.jpg
    14.5 KB · Views: 473
Physics news on Phys.org
chetzread said:
i don't understand the 8/BD = x/EB
I can't see that in your attached images? Is there an image missing?
 
billy_joule said:
I can't see that in your attached images? Is there an image missing?
in post#1
 
billy_joule said:
I can't see that in your attached images? Is there an image missing?
 

Attachments

  • 270.jpg
    270.jpg
    19.6 KB · Views: 476
  • 271.jpg
    271.jpg
    14.5 KB · Views: 410
chetzread said:
in post#1
Yeah, I see the two images in your OP and then again in post #4.

But I don't see this term:
chetzread said:
i don't understand the 8/BD = x/EB
 
  • Like
Likes   Reactions: chetzread
billy_joule said:
Yeah, I see the two images in your OP and then again in post #4.

But I don't see this term:
here
 

Attachments

  • 271.jpg
    271.jpg
    14.5 KB · Views: 423
  • 272.jpg
    272.jpg
    22.8 KB · Views: 443
Ok.
We still don't have the full problem statement as the dimensions of the structure don't appear in any of your three images.
I'm guessing the calc is some geometry to find some unknown length. Maybe E is a typo. Hard to say really, that's why PF homework rules state that you must include the entire question :wink:
 
billy_joule said:
Ok.
We still don't have the full problem statement as the dimensions of the structure don't appear in any of your three images.
I'm guessing the calc is some geometry to find some unknown length. Maybe E is a typo. Hard to say really, that's why PF homework rules state that you must include the entire question :wink:
in second image of post #6
 
chetzread said:
in second image of post #6
I see no dimensions (or angles) on either image in post #6. The second image appears to be part of the worked solution, how could you be expected to solve the problem if the geometry of the truss isn't given?
 
  • Like
Likes   Reactions: chetzread
  • #10
chetzread said:
i don't understand the 8/BD = x/EB
Can anyone explain about it? There's no point E in the diagram...
We need you to post the complete figure and data for the problem as given. There are no dimensions marked on what you have provided.
 
  • Like
Likes   Reactions: chetzread
  • #11
billy_joule said:
I see no dimensions (or angles) on either image in post #6. The second image appears to be part of the worked solution, how could you be expected to solve the problem if the geometry of the truss isn't given?
the full exact question is in photo 271...That's the complete question...
why it's /BD = x/EB?
 
  • #12
chetzread said:
the full exact question is in photo 271...That's the complete question...
Well, then the question is incomplete and unsolvable.
 
  • #13
You don't need dimensions in a statically determinate frame - just the proportions. Guessing that the left hand triangle is in a 3/4/5/ proportion, the figures 6 and 8 make sense. The choices of forces as multiples of 14 suggest the question is looking for an answer that can be achieved without a calculator. The suggested reactions are wrong in my opinion and this reinforces the notion that it is useless to look for internal forces if the external reactions are incorrect. The external reactions should have been checked, for example by taking moments about any point not already used to obtain tham.
 

Similar threads

Calculate Force Member in Truss
  • · Replies 2 ·
Replies
2
Views
2K
Having trouble calculating reaction forces for this truss.
  • · Replies 7 ·
Replies
7
Views
3K
Truss Method of Joints: Solving Unequal Member Forces
  • · Replies 2 ·
Replies
2
Views
2K
Efficient way to solve truss by hand
  • · Replies 7 ·
Replies
7
Views
4K
How Do You Calculate Forces in Truss Members?
  • · Replies 1 ·
Replies
1
Views
2K
Statics - Compression and tension forces in a truss
  • · Replies 2 ·
Replies
2
Views
7K
Are These Calculations for the Statically Indeterminate Truss Correct?
  • · Replies 2 ·
Replies
2
Views
3K
Solving an Internal Indeterminate Truss Problem
  • · Replies 1 ·
Replies
1
Views
2K
How Do X-Braces Affect Indeterminate Truss Analysis?
  • · Replies 2 ·
Replies
2
Views
3K
Designing a Truss: Calculating Forces & Loads
  • · Replies 1 ·
Replies
1
Views
3K