Why Does This Statics Problem Not Specify Resultant Force Direction?

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Discussion Overview

The discussion revolves around a statics problem where the direction of the resultant force is not specified. Participants are exploring the implications of this lack of specification and attempting to clarify their understanding of the problem and their solutions.

Discussion Character

  • Homework-related
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions whether the problem is flawed due to the unspecified direction of the resultant force, suggesting a potential misunderstanding of the problem's requirements.
  • Another participant notes that there are too many unknowns unless the direction of the resultant force is assumed to be in a specific direction ("u").
  • A different participant points out a possible error in the calculations related to the force component Fry, suggesting that the sine function may have been overlooked.
  • Another participant proposes a method to calculate the angle of the resultant force (β) using two equations derived from the components in the x and y directions, indicating that there are knowns and unknowns that can be worked with.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the unspecified direction of the resultant force, with some suggesting assumptions must be made while others question the problem's validity. The discussion remains unresolved regarding the best approach to take.

Contextual Notes

Participants highlight the presence of multiple unknowns and the need for assumptions, particularly regarding the direction of the resultant force. There are also indications of potential calculation errors that have not been definitively resolved.

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Homework Statement



http://imgur.com/a/FyekZ
I took the liberty of uploading everything. The first picture is the question, while the other two is my attempt at answering it in two parts. What I do not understand is what I did wrong or where I went wrong.
I also would like to know why, unlike many other questions from the text, this question does not specify in which direction the resultant force is directed. Is the question wrong, or am I supposed to go about this in a different manner?

EDIT: If you cannot see the full image, please click the gear icon (top right of each image - gear appears when you have the mouse over the image) and select view full resolution.

Homework Equations



See above.

The Attempt at a Solution



Please see above.
 
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Last edited:
Ok so there appears to be too many unknowns unless you assume the resulting force is to be in the "u" direction.
 
I think you may have made an error in the calc for Fry. Did you forgot to divide by Sin(28)?
 
Actually it looks like you can calculate the angle of the resultant. Call that β then..

In x..

FR*Cos(β) = F1*Cos(θ) - F2*3/5 + F3*Cos(45)
so
F1*Cos(θ) = FR*Cos(β) + F2*3/5 - F3*Cos(45) ...(1)

In y..

FR*Sin(β) = F1*Sin(θ) + F2*4/5 - F3*Sin(45)
so
F1*Sin(θ) = FR*Sin(β) - F2*4/5 + F3*Sin(45)...(2)


Knowns F2, F3, FR, θ
Unknowns F1 and β

We have two equations and two unknowns.
 

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