How to determine direction of forces in free body diagrams?

AI Thread Summary
To determine the direction of forces in free body diagrams, focus on breaking the reaction force into x and y components. The sign of the x-component indicates the direction: a positive value means the force is directed to the right (Direction B), while a negative value indicates it points to the left (Direction A). It's suggested to prioritize solving for the forces without worrying about their initial direction. Once the stability conditions are applied, the correct magnitude and direction will emerge. Understanding these components is crucial for accurate analysis in physics.
Yoriko
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For instance, in the below diagram:

[PLAIN]http://img101.imageshack.us/img101/3205/59914396.png

How do you know if the reaction force on the beam is in Direction A or B? How do you determine the correction direction?
 
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Don't worry about getting the correct direction. Break up the reaction force into x and y components, and solve for the forces that way. If the x-component turns out to be positive (towards the right), then the correct direction is B. If the x-component is negative, then it's A.
 
yes, I agree with redbelly, don't bother about the direction now. since the movement of the beam is being prevented in x and y direction at the hinge, just show forces in x and y direction. then when you use stability conditions, you will get correct magnitude and the direction anyway
 
Redbelly98 said:
Welcome to Physics Forums.

Don't worry about getting the correct direction. Break up the reaction force into x and y components, and solve for the forces that way. If the x-component turns out to be positive (towards the right), then the correct direction is B. If the x-component is negative, then it's A.

Ok thanks!:biggrin:
 
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