- #1
Need clarification about two-force member
- Context: Undergrad
- Thread starter Femme_physics
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Discussion Overview
The discussion revolves around the concept of a two-force member in mechanics, specifically addressing the direction of force vectors at a support point (point B) in relation to applied forces. Participants seek clarification on the behavior of forces acting on a lever system.
Discussion Character
- Conceptual clarification
- Debate/contested
Main Points Raised
- Some participants express confusion about the direction of the force vector emerging from support point B, questioning why it points towards the applied force rather than in the opposite direction.
- One participant suggests that if the hinge-point or screw at B were not present, the lever would break apart in the direction of the applied force, implying that the vector should reflect this by pointing in the opposite direction.
- Another participant clarifies that the force on the piece BD from the lever is directed to the right, while the force from the piece BD on the lever is directed to the left, indicating a reactionary force relationship.
Areas of Agreement / Disagreement
Participants do not reach a consensus on the interpretation of the force vectors at point B, indicating that there are competing views regarding the directionality of forces in the system.
Contextual Notes
The discussion highlights potential misunderstandings regarding free body diagrams and the representation of forces, but does not resolve these issues or clarify assumptions about the system's configuration.
- #2
tiny-tim
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Dory said:
Hi Dory!
I don't understand what's worrying you
…the piece BD is being pulled one way by the lever, and the opposite way by the reaction force at the wall …
isn't that as it should be?
- #3
Femme_physics
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Yes-- opposite reaction at the WALL, but check out point B -- if that hinge-point or screw wasn't there the lever would break apart to where the force is pulling at! So, shouldn't its vector also be pointing the opposite direction? Instead, it's pointing to where the force is pointing!
This is what confusing me...the fact that the B point is positive on the X axis and not negative
This is what confusing me...the fact that the B point is positive on the X axis and not negative
- #4
tiny-tim
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Yes, the force from the piece BD on the lever is to the left, and so the force on the piece BD from the lever is to the right …
the free body diagram is for forces on the piece BD.
the free body diagram is for forces on the piece BD.
- #5
Femme_physics
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Ohhhhhhhhhhhhhhhhhhhhhhhhh...done deal.*smacks forehead* Thanks.
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