Is the Sum of All Moments Zero at Any Point if Zero at Point A in 2-D Mechanics?

In summary, the sum of all moments about a point A of a body being 0 does not necessarily mean it will be 0 anywhere else on the body. It depends on the specifics of the problem and the existence of equilibrium. If there is equilibrium, then the sum of all moments around any point will be 0.
  • #1
kasse
384
1
If the sum of all moments about a point A of a body is 0, will it then be 0 anywhere else on the body? (I'm working in 2-D)
 
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  • #2
Maybe. It depends entirely on the particulars of the problem.
 
  • #3
Not necessarily.
 
  • #4
So I don't necesarrily have equilibrium if I find that F(res) = 0 and that M(A) = 0 ? What more do I need to `show eq.?
 
  • #5
I assume that it works the other way around: if I know that there's equilibrium, then the sum of all moments around any point is 0.
 
  • #6
kasse said:
I assume that it works the other way around: if I know that there's equilibrium, then the sum of all moments around any point is 0.
That is correct. With respect to your previous post, it depends on the situation, as Russ said in your other thread.
 
  • #7
kasse said:
If the sum of all moments about a point A of a body is 0, will it then be 0 anywhere else on the body? (I'm working in 2-D)

kasse, do not multiple post the same question across multiple forums. I've merged in the thread that you started in Classical Physics with the same question.
 

1. What is the "Sum of all moments problem" in physics?

The "Sum of all moments problem" is a concept in physics that involves calculating the sum of all the individual moments acting on an object. Moments are rotational forces or torques that cause an object to rotate around a fixed point. This problem is important in understanding the overall motion and stability of an object.

2. How is the "Sum of all moments problem" different from the "Sum of forces problem"?

The "Sum of all moments problem" focuses on rotational forces, while the "Sum of forces problem" focuses on linear forces. In other words, the "Sum of all moments problem" deals with the rotational motion of an object, while the "Sum of forces problem" deals with the overall motion of an object.

3. What are some real-life examples of the "Sum of all moments problem"?

Some examples of the "Sum of all moments problem" in everyday life include balancing a seesaw, opening a door, and turning a steering wheel. In each of these situations, there are multiple moments acting on the object that need to be balanced in order to achieve the desired motion.

4. How do you solve the "Sum of all moments problem"?

To solve the "Sum of all moments problem", you need to identify all the forces and moments acting on the object, as well as their distance from the fixed point. Then, using the principle of moments, you can calculate the sum of all the moments and determine if the object is in equilibrium or not.

5. Why is understanding the "Sum of all moments problem" important in engineering?

The "Sum of all moments problem" is important in engineering because it allows for the design and analysis of stable and balanced structures. Engineers use this concept to ensure that buildings, bridges, and other structures can withstand the forces and moments acting on them without collapsing or becoming unstable.

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