Find x-Bar Location for Distributed Loading | Torque Calculation

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Discussion Overview

The discussion revolves around determining the location of the centroid for a distributed loading represented by triangular loads on a beam, specifically in the context of calculating torque and resultant forces. Participants explore the properties of centroids for different shapes, particularly right triangles and rectangles, and how these relate to the problem at hand.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant calculates the resultant forces from the distributed loading and attempts to solve for the location of x-bar using torque equations.
  • Several participants discuss the centroidal location of right triangles, suggesting that the distributed load can be divided into two triangular loads.
  • There is a query about the centroid location of a triangle, with references to the centroid of rectangles and the need for clarification on the 1/3 and 2/3 rule.
  • Some participants express uncertainty about which side of the triangle corresponds to the 1/3 and 2/3 distances from the pointy end to the base.
  • One participant asserts that the centroid would be located at 2/3 of the base length from the pointy end, while another questions the application of this rule based on triangle orientation.
  • Clarifications are made regarding the use of 1/3 for triangles and 1/2 for rectangles, depending on the reference point for calculations.

Areas of Agreement / Disagreement

Participants express varying degrees of understanding regarding the centroid locations for different shapes, and there is no consensus on the application of the 1/3 and 2/3 rule based on triangle orientation. The discussion remains unresolved regarding the specific application of these concepts to the problem presented.

Contextual Notes

Participants reference the need for visual aids to clarify the orientation of the triangles and the corresponding centroid calculations, indicating that assumptions about the triangle's position may affect the results.

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Homework Statement



Replace the distributed loading with an equivalent resultant
force, and specify its location on the beam measured from
point O.

W = 3 kn/m

Homework Equations



F*xbar = torque

The Attempt at a Solution



I got the resultant forces:

(1/2)*3*3 = 4.5 kn
(1/2)*1.5*3 = 2.25 kn

4.5 + 2.25 = 6.75 kn

I know my general equation is:

6.75*xbar = torque

I want to solve for xbar.

xbar should equal 2.5m
 

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What's the centroidal location of a right triangle? Your distributed load can be broken up into two triangular loads.
 
SteamKing said:
What's the centroidal location of a right triangle? Your distributed load can be broken up into two triangular loads.

I'm unsure, could you explain it to me?
 
If the centroid of a rectangle is located at half the length or half the depth, what is the centroid of a triangle?

If you're still stumped, you can always google 'centroid of right triangle'
 
SteamKing said:
If the centroid of a rectangle is located at half the length or half the depth, what is the centroid of a triangle?

If you're still stumped, you can always google 'centroid of right triangle'

If I multiply both distances by 1/3, I still do not get the proper answer.
 
I see, so when I approach the triangle from the one side I have 1/3 so the rest must be 2/3. But how do I know which is the 1/3 side and which is the 2/3 side?
 
shreddinglicks said:
I see, so when I approach the triangle from the one side I have 1/3 so the rest must be 2/3. But how do I know which is the 1/3 side and which is the 2/3 side?

If you have a right triangle with the pointy end at O, how far from O will the centroid be, 1/3 of the length of the base or 2/3 of the length of the base?
Remember, the location of the centroid coincides with the balance point of the triangle.
 
SteamKing said:
If you have a right triangle with the pointy end at O, how far from O will the centroid be, 1/3 of the length of the base or 2/3 of the length of the base?
Remember, the location of the centroid coincides with the balance point of the triangle.

It would have to be 2/3.

So, if I had a problem where I had to find, say a location at point, "A" that was directly under W. The distance would then be 1/3 for each triangle?
 
shreddinglicks said:
It would have to be 2/3.

So, if I had a problem where I had to find, say a location at point, "A" that was directly under W. The distance would then be 1/3 for each triangle?

I'm not sure what you are asking here. The choice of whether to use 1/3 or 2/3 of the length of the base as the centroid depends on the orientation of the triangle.
 
  • #10
SteamKing said:
I'm not sure what you are asking here. The choice of whether to use 1/3 or 2/3 of the length of the base as the centroid depends on the orientation of the triangle.

I meant a situation like the one pictured. I would use 1/3 for each triangle, and I would use 1/2 for the rectangle, correct?
 

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  • #11
shreddinglicks said:
I meant a situation like the one pictured. I would use 1/3 for each triangle, and I would use 1/2 for the rectangle, correct?

1/3 of the base for each triangle would be OK, as long as the reference was taken about a vertical line running thru the support at B.
 
  • #12
I see, thanks for your help!
 

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