Statics: Finding the moment on point B?

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Homework Help Overview

The discussion revolves around determining the moment about point B due to three forces acting on a beam, with a focus on calculating the moments using the equation M = F*d⊥. Participants are exploring the components of the forces and their respective distances from point B.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to find the components of the forces acting on the beam and are questioning the correctness of their calculations. There is a focus on determining the perpendicular distances for each force to calculate the moments accurately.

Discussion Status

Some participants have provided calculations for the force components and are discussing the distances involved. There is an ongoing exploration of the distances from point B to each force, with one participant realizing a specific distance for F1. The discussion reflects a collaborative effort to clarify the setup and calculations without reaching a definitive conclusion.

Contextual Notes

Participants are working with a figure that is referenced but not visible in the discussion. There is mention of a sign convention and the right-hand rule, indicating that assumptions about these conventions are being examined.

Vanessa Avila
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Homework Statement


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[/B]
Determine the moment about point B of each of the three forces acting on the beam.

Homework Equations


M = F*d⊥

The Attempt at a Solution


I went and found the components for each of the forces. Please double check it if I did them right:

F1 :
Fx = 0
Fy = 375 lb

F2:

Fx = -500(3/5)lb = -300lb
Fy = -500(4/5)lb = -400lb

F3:
Fx = 160cos30° = 138.6lb
Fy = -160sin30° = -80lb

If those components are right, I'm having trouble finding their perpendicular distances.
 
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Based on the figure above is the
F*d⊥ for each of the forces are (without the sign convention/right hand method applied):
F1
Fx1 = 0
Fy1 = 375lb*19ft

F2
Fx2 = -300lb(0.5ft)
Fy2 = -400lb(19ft)

F3
Fx3 = 138.6lb(0.5ft)
Fx3 = -80lb(19ft)

I got 19ft by adding the three dimensions below the beam. Is that correct?
 
Label forces with F, and moments (force times distance) with M.
To calculate the moment of force F1 about point B, how far is F1 from point B?
 
David Lewis said:
Label forces with F, and moments (force times distance) with M.
To calculate the moment of force F1 about point B, how far is F1 from point B?
Ahh! 11 ft!
 

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