Find Moment and Force in 3-D Plane

In summary, There are two ways to find the moment about an axis in a 3-d plane when a force is being applied: drawing the "r" vector from the axis to the point of where the force is being applied, and reversing the direction of the r vector. While there are infinite ways to draw the r vector that produce equal moment, reversing its direction will result in an equal but opposite moment. A program in Octave can be used to address this issue, or it can be converted to other languages.
  • #1
megr_ftw
71
0
I really don't need an answer to a question but I'm trying to show there are two ways to find the moment about an axis in a 3-d plane when a force is being applied.
I know you draw the "r" vector from the axis to the point of where the force is being applied, but sometimes there are two different ways to draw the r vector. My question is that the moments should be equal regardless where the r vector is?
 
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  • #2
megr_ftw: What do you mean by "two ways"? Did you mean to say "many ways"? If so, and if I am interpreting your question correctly, I think the answer is yes, there are infinite ways to draw the r vector that produce equal moment. And there is a program that might address this issue in post 2195467 (post 6), which you can use in Octave (free). Or you can convert it to any other language.

However, if you reverse the direction of the r vector, it reverses the sign of the moment, which is not equal but opposite.
 
  • #3
usually the head of the force joins the tail of the vector r
 

FAQ: Find Moment and Force in 3-D Plane

1. What is a moment in a 3-D plane?

A moment in a 3-D plane is a measure of the tendency of a force to rotate an object around an axis. It is defined as the product of the magnitude of the force and the distance from the axis of rotation to the line of action of the force.

2. How is a moment represented in a 3-D plane?

A moment in a 3-D plane is typically represented by a vector, with a direction and magnitude. The direction of the moment vector is perpendicular to the plane of rotation, and the magnitude is calculated using the right-hand rule.

3. What factors affect the moment in a 3-D plane?

The moment in a 3-D plane is affected by the magnitude of the force, the distance from the axis of rotation to the line of action of the force, and the direction of the force relative to the axis of rotation.

4. How do you calculate the moment in a 3-D plane?

To calculate the moment in a 3-D plane, you can use the formula M = r x F, where M is the moment, r is the position vector from the axis of rotation to the line of action of the force, and F is the force vector. Alternatively, you can use the cross product of the force and distance vectors to determine the moment.

5. What is the difference between a moment and a force in a 3-D plane?

A moment and a force are both vectors in a 3-D plane, but they have different effects on an object. A force causes linear motion, while a moment causes rotational motion. Additionally, a force acts through a single point, while a moment acts through an axis of rotation.

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