Is My Free Body Diagram for a Frame Accurate?

[YehiaMedhat]

Homework Statement

Can you check my free body diagrams for the whole frames

Relevant Equations

$\sum F_y=0,\sum F_x=0$

can you check if I sketched it correctly?
And please if you know any good resources refrence it.

 

[Lnewqban]

Welcome, @YehiaMedhat !

It seems to me that P is missing, as well as location of D.
Note that for the armature not to collapse, the L-shaped element BC must be rigid and resisting an internal moment.

 

[YehiaMedhat]

More explanation please.
And where could i find info i need for this?

 

[phinds]

More explanation please.

The joint where B and C meet is the only rigid joint in the structure. Can you not see how the whole thing would just fold downwards against the wall if BC is not rigid?

 

[YehiaMedhat]

It seems that i don't even understand what rigid body means

 

[phinds]

It seems that i don't even understand what rigid body means

It means a body for which none of the parts can move relative to each other. Only the whole body can move.

 

[YehiaMedhat]

Well I understand that but why there's an internal moment and where i should put on the sketch.
I'm sorry but all the mechanics is confusing so I try hard to gather informed together

 

[phinds]

Well I understand that but why there's an internal moment and where i should put on the sketch.
I'm sorry but all the mechanics is confusing so I try hard to gather informed together

It seems to me that your problem here is that you don't understand the fundamentals of simple joints yet, so a problem this complex is beyond you. I recommend studying the basic more.

 

[YehiaMedhat]

Can you refrence a specific object.
Cause I actually did revise from the text book and online tutorials about fbd and frames in general

 

[Lnewqban]

Well I understand that but why there's an internal moment and where i should put on the sketch.
I'm sorry but all the mechanics is confusing so I try hard to gather informed together

Clarification:
You don't need to put any internal force on the sketch, as a FBD only shows external forces on each member.
That includes force P, which you have not shown.

Please, see:
https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/5-7-drawing-free-body-diagrams/

and

https://courses.lumenlearning.com/s.../chapter/12-2-examples-of-static-equilibrium/

Sorry about the induced confusion.
I just tried to imply that the L=shaped member BC could be replaced with a straight string, rope or chain, without affecting the static balance of the armature.

 

[YehiaMedhat]

That's great. Thanks for help Mr. Lnewqban and Mr. Phindin

 

[Lnewqban]

That's great. Thanks for help Mr. Lnewqban and Mr. Phindin

You are welcome.

In these problems, the first step is to treat the armature as a solid regarding forces and reactions acting on it.
For that, you use the three equations of balance of x-forces, y-forces and moments that you know.

In that way, you can find the values of the reactions (at points A and B in this case).
You can then use those calculated values to solve the rest of the questions in the problem (forces at connections of links).

If interested, please see this presentation:
https://www.iitg.ac.in/rkbc/me101/Presentation/L-06-08.pdf

 

[YehiaMedhat]

That's great.