Statics free body diagram (frames and machines)

In summary: In order to get the reactions from the wall, you need to add a second free body diagram for the wall.In summary, the student has drawn a free body diagram for each member incorrectly. They need to add a second free body diagram for the wall in order to show the reactions from the wall.
  • #1
lc99
161
3

Homework Statement



upload_2018-4-15_23-44-15.png

Homework Equations


Trying to find the reaction forces at E. But, I am kinda confused about drawing the free body diagram for each member. I know that member AD and CB are two force members. What is wrong with my free body diagram then?

The Attempt at a Solution


upload_2018-4-15_23-47-53.png

i apologize if everything is not straight. Just assume that i tried to draw it straight!
 

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  • #2
lc99 said:
What is wrong with my free body diagram then?
I see two errors in your AB diagram.
You have the load from above wrong, and you show no reaction forces from the wall.
 
  • #3
haruspex said:
I see two errors in your AB diagram.
You have the load from above wrong, and you show no reaction forces from the wall.
Ohh. okay about AB
The distributed load is the area of the two triangles and it is centered at the centroid ?

I also posted another problem very similar to this. I followed the same thing and add the wall(floor) reactions but it ended up being wrong
 
Last edited:
  • #4
lc99 said:
The distributed load is the area of the two triangles and it is centered at the centroid ?
Ok, maybe I misunderstand the diagram. If it is to be interpreted as a load that is a maximum of 4kN/m in the middle, reducing linearly each side, then I agree with your number. Since it only specified 4kN/m I took the load to be constant.
lc99 said:
I followed the same thing and add the wall(floor) reactions but it ended up being wrong
If you post the link I will take a look, but in this thread I believe you need to includ those reactions.
 
  • #5
haruspex said:
Ok, maybe I misunderstand the diagram. If it is to be interpreted as a load that is a maximum of 4kN/m in the middle, reducing linearly each side, then I agree with your number. Since it only specified 4kN/m I took the load to be constant.

If you post the link I will take a look, but in this thread I believe you need to includ those reactions.
here is the link. thank you! :)
https://www.physicsforums.com/threads/statics-problem-free-body-diagram.944966/#post-5980018
 

1. What is a free body diagram?

A free body diagram is a graphical representation of the forces acting on an object or a system. It is used in statics to analyze the equilibrium of a body or a system by showing all the external forces acting on it.

2. How do you draw a free body diagram?

To draw a free body diagram, you must first identify the object or system and all the external forces acting on it. Then, draw a simplified sketch of the object or system, leaving out any unnecessary details. Finally, draw and label all the forces acting on the object or system, including their magnitude, direction, and point of application.

3. What is the difference between a frame and a machine in a free body diagram?

A frame is a structure that is stationary or fixed, while a machine is a structure that is capable of moving. In a free body diagram, frames are represented by a single point, while machines are represented by multiple points connected by lines to indicate their movement.

4. What is the purpose of a free body diagram in statics?

The purpose of a free body diagram in statics is to analyze the forces acting on an object or a system and determine whether it is in equilibrium or not. By drawing and analyzing a free body diagram, we can determine the magnitude, direction, and point of application of each force, and use this information to solve for unknown quantities.

5. Can a free body diagram be used for non-static situations?

No, a free body diagram is only used in statics to analyze the equilibrium of a body or a system. In non-static situations, such as objects in motion, we use other methods such as Newton's laws of motion to analyze the forces acting on the object.

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