Understanding the Direction of AB: Why Negative y?

AI Thread Summary
The discussion centers on the convention of defining moments in physics, specifically why the moment along AB is pointed in the negative y direction. It emphasizes that the choice of positive or negative direction is arbitrary, as long as consistent conventions are applied throughout calculations. If a calculated moment is negative, it indicates that the actual moment acts in the opposite direction from the assumed one. The conversation highlights the importance of understanding these conventions to avoid confusion in physics problems. Ultimately, the direction of moments is determined by the assumptions made during calculations.
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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