Solving for F3 Magnitude and Theta Given F1 and F2

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Homework Help Overview

The problem involves three concurrent forces acting on a post, with a focus on determining the magnitude of force F3 and the angle theta, given that F2 is half the magnitude of F1 and they are oriented at 90 degrees to each other.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationship between the angles formed by F1 and F2, questioning how to express theta in relation to these angles. There are differing opinions on whether to consider the angles with respect to the horizontal or vertical.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of how to relate the angles and components of the forces. Some guidance has been offered regarding the need to express the angles in terms of theta, but no consensus has been reached.

Contextual Notes

Participants are navigating the constraints of the problem setup, including the requirement for the resultant force to be zero and the specific relationships between the forces.

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The three concurrent forces acting on the post produce a resultant force of 0. If F2 = 0.5F1, and F1 is to be 90 degrees from F2 as shown, determine the required magnitude F3 expressed in terms of F1 and the angle theta.


I am having no troubles finding the magnitude of F3, however, I am having trouble understanding how to get theta. Apparently the angle formed by F1 and F2, plus ninety degress, gives you the answer. However, I'm not seeing the relationship. Help?
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Use theta to find the angle that F2 (and F1) makes with the horizontal.
 
Wouldnt you want to find the angle that F2 (and F1) makes with the vertical, then add 90 degrees to find theta?
 
quantum_enhan said:
Wouldnt you want to find the angle that F2 (and F1) makes with the vertical, then add 90 degrees to find theta?
That also would work. Give it a try.

Express the angle that F1 and F2 make with the vertical or the horizontal in terms of theta. Then you can solve for theta.
 
For the vectors to cancel out, the combination of F1 and F2 must result in a vector having the same magnitude as F3 but having opposite direction.

So, to start, find the x-components of F1 and F2. Add them together to get the magnitude of F3. Then substitute what you know about the angles.
 

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