Statics- Resultant couple moment

Click For Summary

Homework Help Overview

The discussion revolves around calculating the resultant couple moment from multiple forces acting on a system, specifically focusing on the forces F1, F2, F3, and F4. The subject area is statics, with an emphasis on vector moments and their components.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the individual moments generated by each force and express uncertainty regarding the calculation of the moment for F4. There is a focus on the directionality of the forces and their components in the xy plane.

Discussion Status

Some participants have provided insights regarding the direction of the F4 couple, suggesting that it has both x and y components. There appears to be a productive exchange of ideas, with some clarification on the interpretation of the forces leading to a better understanding of the problem.

Contextual Notes

Participants mention discrepancies in calculations, particularly regarding the distance used in the moment calculations. There is also a reference to a specific value that should be achieved, indicating a target outcome without confirming it as a definitive solution.

rico22
Messages
51
Reaction score
0

Homework Statement


If F_1 = 100N , F_2 = 120N and F_3 = 80N , determine the magnitude and coordinate direction angles of the resultant couple moment.

Homework Equations


M=Fd
M=r x F
MR=Ʃ(r x F)


The Attempt at a Solution


I found the couple moment for each force:
M1=F1d=100(0.2) or (-20j using right hand rule)
M2=F2d=120(0.2) or +24i
M3=F3d=80(0.2) or -16k
M4=this is what I am having problems with...not sure how to get the moment for F4... if do 150(.3)(cos30)=38.97 i get the wrong resultant.

The correct answer should be (MC)R=71.9 Nm...
Any help would be greatly appreciated.
 

Attachments

  • Hibbler_ch4_p95.jpg
    Hibbler_ch4_p95.jpg
    8.9 KB · Views: 1,016
Physics news on Phys.org
hi rico22! :smile:
rico22 said:
The correct answer should be (MC)R=71.9 Nm...

i don't get 71.9 unless i use .33 instead of .3 :redface:
 
Note that the F4 couple is not in the x-direction. It is parallel to the xy plane but it has both x and y components which you will need to work out.
 
  • Like
Likes   Reactions: 1 person
TSny said:
Note that the F4 couple is not in the x-direction.

ooh, i didn't notice that! :redface:

i read the axis of that pipe, and the short line above the positive x-axis, as one continuous straight line! :rolleyes:

yes, now i get 71.9 … thanks, Tsny :smile:​
 
thanks for the replies guys...
 

Similar threads

Determining the magnitude of the resultant couple
  • · Replies 2 ·
Replies
2
Views
4K
Engineering Hand tool boundary conditions - Forces determination
  • · Replies 3 ·
Replies
3
Views
2K
What are the coordinate direction angles for the resultant couple moment?
  • · Replies 4 ·
Replies
4
Views
7K