Understanding the Direction of AB: Why Negative y?

In summary, the direction of the moment along AB is a matter of convention and it doesn't affect the calculation as long as the convention is applied consistently. Whether it is positive or negative depends on how it was assumed and if the answer is negative, then the actual direction was opposite.
  • #1
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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  • #2
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.
 
  • #3
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
 
  • #4
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.
 
  • #5
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
 

1. Why is the y-value negative in the direction of AB?

The negative y-value in the direction of AB signifies that the direction is moving downwards on the y-axis. This means that as the value of x increases, the value of y decreases.

2. Can the direction of AB have a positive y-value?

Yes, the direction of AB can have a positive y-value if the line is moving upwards on the y-axis. This means that as the value of x increases, the value of y also increases.

3. How is the direction of AB determined?

The direction of AB is determined by the slope of the line. If the slope is positive, the line will have a positive y-value, and if the slope is negative, the line will have a negative y-value.

4. What does a zero y-value in the direction of AB indicate?

A zero y-value in the direction of AB indicates that the line is parallel to the x-axis. This means that as the value of x increases, the value of y remains constant.

5. Why is it important to understand the direction of AB?

Understanding the direction of AB is important in order to accurately interpret the relationship between two variables. It also helps in determining the direction of change and making predictions based on the given data.

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