ok I am studying free body diagrams, i alredy understand how to obtain the force

Question

ok I am studying free body diagrams, i alredy understand how to obtain the forces but there is something that still concerns me.

is there only one way to orient the forces in a free body diagram or is there different ways? does the orientation of the forces in a fbd matter?

I have an example from the book where sketch #1 is th correct answer according to the book and sketch #2 is my free body diagram. I want to know if it is also correct and if not why?

please give good feedback since I really need to understand free body diagrams.

look at picture attached.

ok I am studying free body diagrams, i alredy understand how to obtain the forces but there is something that still concerns me. is there only one way to orient the forces in a free body diagram or is there different ways? does the orientation of the forces in a fbd matter? I have an example from the book where sketch #1 is th correct answer according to the book and sketch #2 is my free body diagram. I want to know if it is also correct and if not why? please give good feedback since I really need to understand free body diagrams. look at picture attached

Explanation / Answer

There is nothing wrong with what you drew... see when we draw the fbd with unknown internal forces or reactions we are basically assuming directions and there is nothing wrong with the directions you choose.....they don't matter at all upto that point till the forces are unknown..... suppose you have assumed a reaction to be acting toward left and the book assumes it to be towards right then after all the computations you'll get a negative value and the book solution will show a positive value if the force actually happens to be acting towards right........ Now this negative value that you get autamatically says that the force is towards right.......so there is nothing wrong with what you drew.....the same is true for all sorts of unknown variables be it deflection, slope or anything. If you assume the correct directions ie the direction in which you assumed you'll have to deal with positive values only as in the end ie after getting the results u'll have to redraw everything according to the results you get and this result would be the same irrespective of what you initially assumed

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