Understanding the Direction of AB: Why Negative y?

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Homework Help Overview

The discussion revolves around understanding the direction of a moment along a line designated as AB, specifically why it is indicated as pointing in the negative y direction rather than the positive. The subject area involves concepts of mechanics and conventions in physics regarding forces and moments.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the reasoning behind the directionality of moments, questioning the conventions used to define positive and negative directions. There is an emphasis on understanding how assumptions affect the interpretation of results.

Discussion Status

The discussion is ongoing, with participants expressing confusion and seeking clarification on the conventions of directionality in moments. Some guidance has been offered regarding the nature of assumptions, but there is no clear consensus on the reasoning behind the negative designation.

Contextual Notes

Participants are grappling with the implications of assumed directions and the potential for differing interpretations based on those assumptions. There is a noted lack of explicit information regarding the specific setup or conditions of the problem.

Luongo
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Why is the moment along AB pointed in the negative y direction? why not positive how can you tell?
 

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Why wouldn't it be pointed in the negative direction? It's all a matter of convention. Actually, it doesn't matter what you choose to be positive or negative, as long you apply the same convention to all moments and forces you're taking into account in a calculation.
 
radou said:
Why wouldn't it be pointed in the negative direction? It's all a matter of convention. Actually, it doesn't matter what you choose to be positive or negative, as long you apply the same convention to all moments and forces you're taking into account in a calculation.


i don't understand
 
Luongo said:
i don't understand

It just means that they assumed a direction. If you work it out and and the answer for the moment is negative, then the moment was actually acting in the opposite direction.
 
rock.freak667 said:
It just means that they assumed a direction. If you work it out and and the answer for the moment is negative, then the moment was actually acting in the opposite direction.

WHY negative? why not positive then there's only 1 moment
 

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