Direction of Moment: 1200N at A- Clockwise or Counterclockwise?

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Homework Help Overview

The discussion revolves around the direction of the moment produced by a 1200 N force at point A, specifically whether it is clockwise or counterclockwise. Participants are examining the implications of these directions in the context of equilibrium and reaction moments in a beam setup.

Discussion Character

  • Conceptual clarification, Assumption checking, Mixed

Approaches and Questions Raised

  • Participants are exploring the relationship between the applied force and the resulting moments, questioning how the direction of the moment relates to equilibrium conditions. There is a focus on the distinction between the moment due to the applied force and the reaction moment at the beam's connection to the wall.

Discussion Status

The discussion is ongoing, with participants providing insights into the nature of moments and their directions. Some have offered clarifications regarding the relationship between the moments and their respective directions, while others are questioning the assumptions made in the original statements.

Contextual Notes

There appears to be some confusion regarding the interpretation of the moments and their directions, as well as the implications of taking moments in different directions for the sake of analysis. The presence of a drawing is noted, which may influence the understanding of the problem setup.

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Homework Statement


Why shouldn't the direction of moment for 1200n at A =clockwise? Why the book gave counterclockwise?

Homework Equations

The Attempt at a Solution

 

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It depends if you are talking about the moment of the force (1200 N), which is turning clockwise or if you are looking at the reaction moment in the connection of the beam to the wall (MA), which has to turn counterclockwise to establish the equilibrium. Two moments of the same size in two different directions.

EDIT: Sorry, I didn't look at the drawing well: The moment MA of course must be the sum of the moments produced by the force (1200 N) and the weight of the beam (both with clockwise direction).
 
Last edited:
stockzahn said:
EDIT: Sorry, I didn't look at the drawing well: The moment MA of course must be the sum of the moments produced by the force (1200 N) and the weight of the beam (both with clockwise direction).
Well, no, as you wrote in the first paragraph MA would be equal and opposite to the sum of those two moments, hence anticlockwise.
Anyway, it really doesn't matter which way it is presumed to be. MA could be taken to be clockwise, and the equations written accordingly. It would then turn out to have a negative value.
 
the correct
haruspex said:
Well, no, as you wrote in the first paragraph MA would be equal and opposite to the sum of those two moments, hence anticlockwise.
Anyway, it really doesn't matter which way it is presumed to be. MA could be taken to be clockwise, and the equations written accordingly. It would then turn out to have a negative value.
the correct moment would be in clockwise direction , right ? the anticlockwise in merely the reaction of the moment produced which is in opposite direction , am i right ?
 
haruspex said:
[] ... MA would be equal and opposite to the sum of those two moments, hence anticlockwise.

That was what I meant to say in my EDIT. Sorry for the ambigous expression.
 
goldfish9776 said:
the correct moment would be in clockwise direction , right ? the anticlockwise in merely the reaction of the moment produced which is in opposite direction , am i right ?
In the textbook extract you posted, MA is the reaction moment. Read it carefully. There is no error there.
 

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