Trouble Understanding Moment Calculations?

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Discussion Overview

The discussion revolves around understanding the signs used in moment calculations, specifically regarding the direction of moments generated by a force acting on a moment arm. The scope includes conceptual clarification and technical reasoning related to mechanics.

Discussion Character

  • Conceptual clarification, Debate/contested

Main Points Raised

  • One participant expresses confusion about the sign convention for moments, believing that a 600 N force acting on the moment arm results in a clockwise (CW) moment, which they think should be negative.
  • Another participant argues that the same 600 N force, when considered, actually produces a counterclockwise (CCW) moment about point C, suggesting a different interpretation of the moment's direction.
  • A third participant reflects on their initial misunderstanding, acknowledging that they initially thought the moment was CW but later recognized it as CCW, indicating a shift in their understanding.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the sign convention for the moment calculation, as there are conflicting interpretations of the direction of the moment generated by the force.

Contextual Notes

There are unresolved assumptions regarding the definitions of clockwise and counterclockwise moments, as well as the specific conditions of the problem that may influence the calculations.

Permanence
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Hi,

I am having trouble understanding how the signs were obtained in the moment calculation.

When I imagine the 600 N force acting on the moment arm, it moves CW which would give it a negative value. When I solve the problem I end up reviving Ay and Cy values that are swapped with the book.
 
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Permanence said:
When I imagine the 600 N force acting on the moment arm, it moves CW which would give it a negative value.
The 600N force is to the right, that's counter clockwise about point C.
 
I thought that I'm suppose to draw a line down from C to the line of action of the force. Then apply the force to that line, and imagine (ignore that)

As I'm writing my response I see that it is CCW. I have no idea why I thought it was CW and was so insistent upon that. Thank you for the reply.
 
You're welcome :smile:
 

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