Centre of Gravity and Centroids

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Discussion Overview

The discussion revolves around understanding the concepts of center of gravity and centroids as presented in two slides. Participants are particularly focused on the mathematical representation of moments and the use of weight in the context of rigid bodies, exploring the relationship between total weight and the weight of individual particles.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on the summation of moments in the x and y directions, specifically questioning the transition from xW to the sum of X times change in W.
  • Another participant notes that W represents the weight of the entire plate or piece of wire, prompting a question about the use of Delta W instead of W itself.
  • A subsequent post suggests that Delta W may refer to the weight of individual tiny particles, which when summed, yield the total weight of the rigid body.
  • Another participant reiterates the idea that Delta W signifies the weight of individual particles, leading to a mathematical expression involving integration.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the use of Delta W and its implications. There is no consensus on why Delta W is used instead of W, and multiple interpretations of its meaning are presented.

Contextual Notes

Participants are working from limited information provided in the slides, which may affect their understanding of the concepts discussed. The discussion includes assumptions about the nature of the rigid body and the particles that compose it.

Who May Find This Useful

Students studying mechanics, particularly those interested in the concepts of center of gravity and centroids, as well as those tackling related homework problems.

DiamondV
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Homework Statement


http://puu.sh/lJgzB/5b877de108.jpg

http://puu.sh/lJgAR/c28393f051.jpg

Can someone please explain these two slides to me? Especially the first one, It seems to be summing the Moments in y and Moments in x. The sum of the moments in y is xW. I understand that but then it says that xW is equal to Sum of X times Change in W. Thats what I don't get. This is like the first page of the notes, there's no other info given. This is all.
EDIT: I've realized that we are assuming that the rigid body is made up of millions of tiny particles each at different distances(x) and different weights(W). So we sum it. But I still don't get why we use Delta W instead of W itself?

Homework Equations

The Attempt at a Solution

 
Last edited by a moderator:
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DiamondV said:

Homework Statement


http://puu.sh/lJgzB/5b877de108.jpg

http://puu.sh/lJgAR/c28393f051.jpg

Can someone please explain these two slides to me? Especially the first one, It seems to be summing the Moments in y and Moments in x. The sum of the moments in y is xW. I understand that but then it says that xW is equal to Sum of X times Change in W. Thats what I don't get. This is like the first page of the notes, there's no other info given. This is all.
EDIT: I've realized that we are assuming that the rigid body is made up of millions of tiny particles each at different distances(x) and different weights(W). So we sum it. But I still don't get why we use Delta W instead of W itself?
Because W is the weight of the entire plate or piece of wire.
 
Last edited by a moderator:
SteamKing said:
Because W is the weight of the entire plate or piece of wire.
Why is Change in W used then?(delta W)
 
Or is the Delta W just signifying the weight of the individual tiny particle that when summed together(sigma) results in the weight of the the rigid body?
 
DiamondV said:
Or is the Delta W just signifying the weight of the individual tiny particle that when summed together(sigma) results in the weight of the the rigid body?
Right. ##W = \int dW ##
 

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