How do I analyze a body with a 14 kip force at a point?

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Homework Help Overview

The discussion revolves around analyzing a body subjected to a 14 kip force at a specific point, focusing on the equilibrium of forces and moments in a two-dimensional plane involving vertical and horizontal components.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the necessity of including reaction forces at point B when detaching members and question how to account for the applied force in their equations. There is also exploration of the number of unknowns versus equations available for solving the problem.

Discussion Status

Participants are actively engaging with the problem, raising questions about the setup and the implications of the applied force on the members. Some guidance is provided regarding the inclusion of forces and moments in the equations, but no consensus has been reached on the final approach.

Contextual Notes

There is a mention of having six unknowns and six equations, indicating a potential balance in the problem setup, but the complexity of the equations and the specific roles of the forces are still under discussion.

fayan77
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Homework Statement


Screen Shot 2019-02-03 at 4.23.19 PM.png


Homework Equations


Using dimensional plane in the vertical y and horizontal x.
##\Sigma##Fx = 0
##\Sigma##Fy = 0
##\Sigma##Mz = 0

The Attempt at a Solution


I have detached the 2 members at B and analyze them both separately. The 14 kip force is throwing me off though. When I detach the body do I still include a Bx and By force at B, on top of the 14 kip force?
 

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fayan77 said:

Homework Statement


View attachment 238247

Homework Equations


Using dimensional plane in the vertical y and horizontal x.
##\Sigma##Fx = 0
##\Sigma##Fy = 0
##\Sigma##Mz = 0

The Attempt at a Solution


I have detached the 2 members at B and analyze them both separately. The 14 kip force is throwing me off though. When I detach the body do I still include a Bx and By force at B, on top of the 14 kip force?
In separating them, yes, you must include equal and opposite sets of Bx, By. For the X force, you just have to include it with one of them. If you need to answer for the values of Bx and By, it matters which you include it in. Looks like it is to be considered as applied to AB. But which you include it in does not affect any other reaction forces.
 
But then I'm still left with 3 equations 4 unknowns. member AB x positive to the right y positive up moment positive counter clockwise.
##\Sigma##Fx=0: Ax+14-Bx = 0
##\Sigma##Fy=0: Ay-By = 0
##\Sigma##MA=0: -14(12) + Bx(12) - By(9) = 0

same with other member
 
fayan77 said:
same with other member
Yes, but how many unknowns do you have altogether?
 
Ax
Ay
Bx
By
Dx
Dy
6 unknowns
 
fayan77 said:
Ax
Ay
Bx
By
Dx
Dy
6 unknowns
And six equations altogether, right?
 
the only ones I could combine are the ones at connection B. However, that 14 Kip force only act on member AB correct?
If so then from member BCD I use
##\Sigma##MD = 0: 10(5)-By(10)-Bx(12) = 0
50 = 10By+12Bx from member BCD
168 = 12Bx-9By from member AB
solving for Bx and By and solve for the rest
 
fayan77 said:
the only ones I could combine are the ones at connection B. However, that 14 Kip force only act on member AB correct?
If so then from member BCD I use
##\Sigma##MD = 0: 10(5)-By(10)-Bx(12) = 0
50 = 10By+12Bx from member BCD
168 = 12Bx-9By from member AB
solving for Bx and By and solve for the rest
Looks right.
 
Thank you
 

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