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Need clarification about two-force member
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In summary, there is confusion about the direction of the vector emerging from the support of B, which is pointing towards the force being applied instead of in the opposite direction. However, it is clarified that this vector represents the force from the lever on the piece BD, not the force on the piece BD itself.
- #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.
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Femme_physics
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Ohhhhhhhhhhhhhhhhhhhhhhhhh...done deal.*smacks forehead* Thanks.
FAQ: Need clarification about two-force member
What is a two-force member?
A two-force member is a structural element that is subjected to only two forces, without any moments or torques. These forces act in opposite directions and along the same line of action, resulting in a net force of zero on the member. Examples of two-force members include simple trusses and cables.
How do I identify a two-force member?
A two-force member can be identified by examining the free-body diagram of a structure. If a member has only two external forces acting on it and these forces are collinear, then it is a two-force member.
What is the difference between a two-force member and a three-force member?
The main difference between a two-force member and a three-force member is the number of forces acting on the member. A two-force member has only two external forces acting on it, while a three-force member has three external forces acting on it. Additionally, the forces on a two-force member are collinear, while the forces on a three-force member are not necessarily collinear.
Why is it important to clarify if a member is a two-force member or not?
Identifying and differentiating between two-force members and three-force members is crucial in structural analysis. The behavior and internal forces of these members are different, and using the wrong assumption can lead to incorrect solutions. It is also important to properly identify two-force members in order to properly design and support a structure.
What are some common mistakes made when dealing with two-force members?
One common mistake is assuming that a member is a two-force member when it is not. This can lead to incorrect solutions and potentially unsafe structures. Another mistake is not considering the internal forces and stresses in a two-force member, which can affect the overall stability and strength of a structure.