Free Body Diagram from Space Diagram

[steve2510]

Homework Statement

http://desmond.imageshack.us/Himg804/scaled.php?server=804&filename=img1.gif&res=medium
I have to change this space diagram into a free body diagram and i am struggling

Homework Equations

The Attempt at a Solution

I have put a reaction force in the the x direction at point J and a rection force in the y direction at point j aswell. I have also done the same at Point E. I don't no if this is right? I'm not sure if there is meant to be a moment force somewhere? Could anyone help?

 

[OldEngr63]

The purpose of the wheel at J is to prevent any horizontal reaction at that point, so the only external force there is vertical. Now at E, the pin will support both a horizontal and vertical force, but no moment, so forces in both directions there are correct.

 

[steve2510]

thanks very much !

 

[Femme_physics]

Are you only asked for a free body diagram?

Because, it's also important you get the vectors direction right, and this you can normally only do with calculations.

While in principle pin E supports both a horizontal and a vertical force, you can see that no horizontal force is applied at the structure. So there is no horizontal force there at E.

Also, you can see that both vertical reactions at J and E will point up, because all the other forces in between them point down.

 

[DeeNos]

I would like to clarify that a free body diagram represents a simplified version of a physical system, in which the external forces acting on the system are shown as vectors. It is used to analyze the forces acting on a body and to determine its motion or equilibrium state. In contrast, a space diagram is a graphical representation of the physical system, showing its components and their relative positions.

To convert a space diagram into a free body diagram, you first need to identify all the external forces acting on the system. In this case, it appears that there are two reaction forces at points J and E. These reaction forces are equal in magnitude and opposite in direction to the forces exerted by the supports at these points. Therefore, your placement of reaction forces at points J and E is correct.

Additionally, you may also need to consider any other external forces acting on the system, such as gravitational force or applied forces. If there are no other external forces, then your free body diagram is complete.

Regarding the concern about a moment force, it is not necessary to include it in a free body diagram unless it is explicitly mentioned in the problem or if the system is in rotational equilibrium. In this case, it does not appear that there is a moment force acting on the system.

I hope this helps clarify the concept of a free body diagram and how to convert a space diagram into one. If you are still struggling, I suggest seeking assistance from your teacher or a tutor.