- #1
Statics problem free body diagram
- Thread starter lc99
- Start date
Click For Summary
Discussion Overview
The discussion revolves around a statics problem involving free body diagrams and the reactions at a hinge in a structural system. Participants are examining the correct representation of forces acting on members connected at a joint, specifically focusing on the independence of forces between different members.
Discussion Character
- Homework-related
- Technical explanation
- Debate/contested
Main Points Raised
- One participant questions why their reactions at hinge A are considered wrong, indicating confusion about the forces acting on different members.
- Another participant asserts that the reaction forces at hinge A for members AB and AC are independent of each other.
- There is a discussion about the correct forces to include in the free body diagram, with one participant suggesting that only Ax and Ay should be represented for member AB.
- Participants debate whether the force from member AC (Fac) should be included in the free body diagram for member AB, with some arguing it should be excluded due to the independence of the members.
- Clarifications are made regarding the nature of forces acting on the members and the implications for drawing free body diagrams.
Areas of Agreement / Disagreement
Participants express differing views on the inclusion of forces in the free body diagram and the independence of reactions at the hinge. There is no consensus on whether Fac should be included or excluded in the diagrams for member AB.
Contextual Notes
Participants are working through the implications of their assumptions about force interactions at the hinge and the representation of two-force members in free body diagrams. Some steps in the reasoning remain unresolved, particularly regarding the treatment of forces between connected members.
- #2
lc99
- 161
- 3
I meant to post this on the physics homework forum if anyone can move it!
- #3
- #4
- 11,326
- 8,755
lc99 said:
I think it is fine here. No need to move it. If you don't get any answers soon, click on my name and send me a message.
- #5
- 42,886
- 10,521
You are mixing up forces on different members. The reaction between the hinge at A and AB is independent of the reaction between that hinge and AC.lc99 said:
- #6
lc99
- 161
- 3
haruspex said:
What do you mean by independent? I'm not sure if i am understanding. :(
For the reaction between hinge A and AB, you have Ax and Ay. for the reacting between hinge A and AC, you have Fac from the two force member.
are both of my drawings wrong?
Last edited:
- #7
- 42,886
- 10,521
Yes, but you have included Fac on the free body diagram for AB.lc99 said:
- #8
lc99
- 161
- 3
isnt that right? the member AC has force on ABharuspex said:
- #9
- 42,886
- 10,521
No, this is my point about their independence. Each spar is tied to the joint independently of the other. It would be exactly the same if they were tied to different joints that happened to be at the same point.lc99 said:
- #10
lc99
- 161
- 3
haruspex said:
so it should just be Ax and Ay?
- #11
- 42,886
- 10,521
Yes.lc99 said:
- #12
lc99
- 161
- 3
Would it be wrong if i leave Ax and Ay off except Fac? If it is, then whenever i see a two force member and a pin together on one joint, i only draw the Ax and Ay?haruspex said:
Do i leave Fac off because Fac is a reaction force to the pins Ax,Ay?
- #13
- 42,886
- 10,521
There is not (or does not need to be) any force between AB and AC. They just happen to be connected to the same hinge. So the free body diagram for one should ignore the presence of the other.lc99 said:
Similar threads
- · Replies 12 ·
- · Replies 13 ·
Engineering
Equilibrium equations of elastic body
- · Replies 31 ·
- · Replies 2 ·
- · Replies 8 ·
- · Replies 3 ·
- · Replies 5 ·