Finding volumes of revolution using centroids

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Discussion Overview

The discussion revolves around the concept of moments in the context of finding volumes of revolution using centroids, as encountered in a Calculus II course. Participants seek clarification on the definition and interpretation of moments, particularly in relation to physical concepts like torque.

Discussion Character

  • Conceptual clarification, Technical explanation

Main Points Raised

  • One participant requests an explanation of what a moment is, indicating a need for conceptual understanding.
  • Another participant provides a mathematical definition of the moment of a function with respect to the origin, expressed as an integral.
  • A different participant expresses familiarity with calculating moments but seeks a deeper understanding of the concept itself.
  • One response defines a moment as a quantity that has a physical interpretation related to the tendency of a force distribution to cause rotation about a reference point.
  • Another participant describes a moment as a vector quantity that relates to an object's ability to rotate about a point, drawing a parallel to torque.

Areas of Agreement / Disagreement

Participants do not reach a consensus on a singular definition of a moment, as some focus on its mathematical representation while others emphasize its physical interpretation. The discussion remains unresolved regarding a unified understanding of the concept.

Contextual Notes

Participants express varying levels of familiarity with the concept of moments, leading to different interpretations and explanations. There is no resolution on the precise definition or implications of moments in this context.

Towk667
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In my Cal II, we're discussing finding volumes of revolution using centroids, which we find using moments of x or y. Can someone explain to me what a moment is?
 
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If you think of a function f(x) defined over the interval from a to b, then the moment of this function with respect to the origin is

M = int( x*f(x) dx) from a to b
 


No, thanks though, I know how to solve for a moment over an interval, I'd like know what a moment actually is.
 


A moment is just that quantity. If you know the definition, then you know what a moment is.

It has a physical interpretation also, but that is not likely be be a part of a calc class. If f(x) represents a force per unit length, then the moment represents the tendency of that force distribution to cause a rotation about the reference point.
 


Moment is essentially a vector quantity that tells you about an objects ability to rotate about a point by some given force at some given distance. If you know what a torque is they're pretty much the same.
 

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