Determine the moment about a given point

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Discussion Overview

The discussion revolves around calculating moments about specific points (A, B, and D) in a mechanics problem. Participants are exploring the application of the moment equation and the necessary distances for various forces acting on a system.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that the leftmost force produces no moment about point A.
  • There is a suggestion to break down the 52 kN force into its vertical and horizontal components to determine the moments accurately.
  • One participant emphasizes the importance of using the perpendicular distance from the line of action of the force to the point of interest when calculating moments.
  • Another participant mentions needing to find the angle in a triangle related to the problem setup.
  • There is a discussion about using a vertical distance of 1.8 m and determining the horizontal distance by adding another length to 7 m.
  • One participant provides specific calculations for the components of the 52 kN force, indicating the need to find angles for accurate distance measurements.
  • A warning is raised about a potentially dangerous link associated with a picture posted in the thread.

Areas of Agreement / Disagreement

Participants generally agree on the initial assessment regarding the leftmost force producing no moment about point A. However, there is ongoing confusion and uncertainty about the correct distances and angles needed for the calculations, indicating that multiple views and interpretations remain unresolved.

Contextual Notes

Participants express uncertainty regarding the distances and angles necessary for calculating moments, indicating that assumptions about the geometry of the problem may not be fully clarified.

wannawin
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Homework Statement


I'm trying to find the moments about points A,B and D respectively.

wafhA.jpg


Homework Equations


Mx= F * d


The Attempt at a Solution


Correct me if I'm wrong, but on point A the leftmost force produces no moment. After that I'm a little confused about what to use for the distances of the other two forces.
 
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wannawin said:

Homework Statement


I'm trying to find the moments about points A,B and D respectively.

wafhA.jpg


Homework Equations


Mx= F * d


The Attempt at a Solution


Correct me if I'm wrong, but on point A the leftmost force produces no moment.
That is correct.
After that I'm a little confused about what to use for the distances of the other two forces.
Breakup the 52 kN force into its vertical and horizontal vector components, applied where the arrow of the 52 kN force is is touching the line. Then remember the golden rule: The moment of a force, or component of that force, is equal to the force, or component of that force, times the perpendicular distance from the line of action of the force, or component of that force, to the point about which you are summing moments.
For example, looking now at the 93 kN force, its line of action is a vertical line. The moment of that force about A is then 93*(___?__), clockwise. Now calculate the moments for each of the force components of the 52 kN force, and add them all up.
 
you may also need to find the angle in the triangle made after a square.
 
sorry rectangle
 
so I can use 1.8m as the vertical distance, but by the way it looks I guess I have to find out the length of x and add it to 7 in order to find the horizontal distance.

zVEWA.jpg
 
For 52 sin 28 its 1.8 m and for 52 cos 28 you have to find the angle to find the distance which should be added with 7 m
 
When I click on the picture posted in post 1, it says, "This web page has been identified as dangerous. For your own safety, please close this window now, and never return to this web site." Just wanted to warn you guys. It might be dangerous.
 

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