How do I know which direction the horizontal force acts

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Discussion Overview

The discussion revolves around determining the direction of horizontal reaction forces in a 3 pin frame within a homework context. Participants explore how to identify the correct labeling of these forces based on the provided diagram and their understanding of reaction forces in relation to applied forces.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses uncertainty about how to label the horizontal reactions HA and HF, noting a belief that reactions should oppose applied forces.
  • Another participant points out that the direction of the horizontal forces has already been indicated in the diagram, suggesting that clarity in the problem description is important.
  • A participant reiterates the need to understand which direction the reaction forces act and seeks information from the diagram to confirm that both HA and HF act to the right.
  • One participant mentions that drawing forces in the wrong direction will result in a negative value in calculations, emphasizing the importance of correct labeling.
  • A later reply indicates that the original poster has resolved their issue and appreciates the assistance received, although the specifics of the solution are not detailed.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the method for determining the direction of the horizontal reaction forces, as there are differing interpretations of the diagram and the principles involved.

Contextual Notes

There is a lack of complete information regarding the diagram and the specific applied forces, which may affect the understanding of the reaction forces. The discussion also highlights the importance of clear problem statements in homework contexts.

Who May Find This Useful

Students working on mechanics problems involving reaction forces in structures, particularly in the context of homework assignments related to statics or structural analysis.

DaiRSquared.
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Homework Statement


I am to find the reactions of a 3 pin frame.

Homework Equations

The Attempt at a Solution


So how do I know which direction to label the horizontal reactions? In the diagram HA and HF are in the same direction, I was under the impression that reactions are opposite to applied force.
Photo 30-04-2015 21 44 56.jpg


I have no problems calculating a solution once i know which direction the reaction occurs.
 
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Uhh, looks like someone has drawn in the direction of the horizontal forces at pins A and F.

This is why PF Rules request that posters provide a complete description of the HW problem and use of the HW template.
 
Yes that was me. I know the method to calculate a solution providing I know which directions the horizontal reaction forces act.

My question was how do I know which direction the reaction forces act or what bit of information in that diagram tells me that HA and HF both act to the Right.
 
DaiRSquared. said:

Homework Statement


I am to find the reactions of a 3 pin frame.

Homework Equations

The Attempt at a Solution


So how do I know which direction to label the horizontal reactions? In the diagram HA and HF are in the same direction, I was under the impression that reactions are opposite to applied force. View attachment 82851

I have no problems calculating a solution once i know which direction the reaction occurs.
If you draw the forces in the wrong direction, you will simply get a negative number in your answer!
 
I have already solved my problem and would have marked it solved if i knew how. Your answer was the one I was looking for, thank you for taking the time to read the problem and reply.
 

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