- #1
Statics problem free body diagram
- Thread starter lc99
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SUMMARY
The discussion centers on the correct interpretation of free body diagrams in statics, specifically regarding the reactions at hinge A for members AB and AC. Participants clarify that the reactions at hinge A, represented as Ax and Ay for AB, are independent of the forces acting on AC, denoted as Fac. The consensus is that including Fac in the free body diagram for AB is incorrect, as each member's forces should be treated independently, regardless of their connection at the same hinge.
PREREQUISITES- Understanding of free body diagrams in statics
- Knowledge of reaction forces at hinges and joints
- Familiarity with two-force members in structural analysis
- Basic principles of equilibrium in mechanics
- Study the principles of free body diagrams in statics
- Learn about the independence of forces in structural mechanics
- Explore the concept of two-force members and their implications
- Review examples of equilibrium conditions in mechanical systems
Students studying statics, mechanical engineers, and anyone involved in structural analysis or mechanics who seeks to improve their understanding of free body diagrams and reaction forces.
- #2
lc99
- 161
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I meant to post this on the physics homework forum if anyone can move it!
- #3
- #4
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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
- 42,802
- 10,495
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
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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
- 42,802
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Yes, but you have included Fac on the free body diagram for AB.lc99 said:
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lc99
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isnt that right? the member AC has force on ABharuspex said:
- #9
- 42,802
- 10,495
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
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haruspex said:
so it should just be Ax and Ay?
- #11
- 42,802
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Yes.lc99 said:
- #12
lc99
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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
- 42,802
- 10,495
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:
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