How do I know which direction the horizontal force acts

AI Thread Summary
To determine the direction of horizontal reaction forces in a 3-pin frame, one must analyze the applied forces and their effects on the system. The reactions at pins A and F (HA and HF) typically act in the same direction as the applied forces, contrary to the assumption that they are always opposite. If the forces are drawn incorrectly, it will result in negative values in calculations, indicating the need for reevaluation. Clear labeling and understanding of the force diagram are crucial for accurate analysis. Ultimately, knowing the correct direction of these forces is essential for solving the problem effectively.
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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