Statics for rod attached to string

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The discussion centers on the analysis of forces and moments in a static system involving a rod attached to a string. Participants clarify that the force at point A does not contribute to the moments about that point, as the focus is on moments rather than forces. Additionally, it is established that resolving forces at a single point, such as point C, is valid in specific contexts, despite common misconceptions about needing to consider the entire system. This highlights the importance of understanding the principles of static equilibrium in mechanics.

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could someone please explain to me why there is no relative force at point a where the rod ab is attached to a

thanks
 

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markosheehan said:
could someone please explain to me why there is no relative force at point a where the rod ab is attached to a

thanks

There is.
In the answer key it has been left out, since it's focusing on the moments about a.
The force at point a does not contribute to the moments about a.
 
thanks

I do not see how they can just resolve forces at point c horizontally and vertically. For these type of questions I was always told you can only resolve forces horizontally and vertically for the whole system not just 1 random point on the system. can you just resolve forces horizontally and vertically for 1 point on all types of questions like these.

I can also not see why/how they can take moments about point b for just point c. again I was always told when taking moments about a point you have to take all forces in the whole system about point c not just the forces at one point in the system.
 

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