Trouble Understanding Moment Calculations?

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SUMMARY

The discussion centers on the confusion surrounding moment calculations, specifically regarding the direction of forces and their impact on moment values. The participant initially believed that a 600 N force acting on a moment arm produced a clockwise (CW) moment, which would yield a negative value. However, upon further reflection, they recognized that the force actually creates a counterclockwise (CCW) moment, leading to a correction in their calculations and alignment with the expected results in the reference material.

PREREQUISITES
  • Understanding of basic mechanics principles, particularly moments and forces.
  • Familiarity with the concept of moment arms in physics.
  • Knowledge of how to determine the direction of moments (clockwise vs. counterclockwise).
  • Ability to interpret and apply static equilibrium equations.
NEXT STEPS
  • Study the principles of static equilibrium in mechanics.
  • Learn about calculating moments using different force orientations.
  • Explore the use of free body diagrams to visualize forces and moments.
  • Review examples of moment calculations in engineering mechanics textbooks.
USEFUL FOR

This discussion is beneficial for students in engineering or physics, educators teaching mechanics, and professionals involved in structural analysis or mechanical design who need to clarify moment calculations.

Permanence
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Hi,

I am having trouble understanding how the signs were obtained in the moment calculation.

When I imagine the 600 N force acting on the moment arm, it moves CW which would give it a negative value. When I solve the problem I end up reviving Ay and Cy values that are swapped with the book.
 
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Permanence said:
When I imagine the 600 N force acting on the moment arm, it moves CW which would give it a negative value.
The 600N force is to the right, that's counter clockwise about point C.
 
I thought that I'm suppose to draw a line down from C to the line of action of the force. Then apply the force to that line, and imagine (ignore that)

As I'm writing my response I see that it is CCW. I have no idea why I thought it was CW and was so insistent upon that. Thank you for the reply.
 
You're welcome :smile:
 

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