Magnitude and Direction of Force

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Homework Help Overview

The discussion revolves around determining the magnitude and direction of a force (F3) in a vector problem involving three forces, with the resultant force given as 20 lb. The original poster indicates that F3 is the smallest force among them.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss using components (Rx and Ry) and the challenges posed by having multiple unknowns in the equations. There is mention of complications arising from the sine and cosine functions involved in the calculations.

Discussion Status

Participants are actively engaging with the problem, questioning the number of unknowns and exploring the relationships between them. Some guidance has been offered regarding squaring and adding components, but there is no explicit consensus on the approach to take.

Contextual Notes

There is an indication that the problem may involve assumptions about angles and the relationships between the forces, which are not fully detailed in the provided information.

chadovP
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Homework Statement



http://img243.imageshack.us/my.php?image=61581222vi0.jpg
http://xs433.xs.to/xs433/08440/untitled601.jpg

I need to find the direction and the magnitude of F3 given only the figure and the resultant force of the 3 vectors =20 lb, plus F3 being the smallest force between all of them.

The Attempt at a Solution



Tried Rx and Ry and squaring them but I have 3 unknows in 1 solution...

any ideas?
 
Last edited by a moderator:
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Welcome to PF!

chadovP said:
Tried Rx and Ry and squaring them but I have 3 unknows in 1 solution...

Hi chadovP! Welcome to PF! :smile:

(have a theta: θ :wink:)

I don't get it :confused: …

the only two unknowns are F3 and θ …

what unknowns did you have? :smile:
 
yes but there are sin θ and cos θ which makes the equation very complicated.
 
chadovP said:
yes but there are sin θ and cos θ which makes the equation very complicated.

ah!

but that's still only one unknown!

Hint: square, and add. :wink:
 
2 unknows mate! F3 and the angle...
so i have f3 sqaured and the angle in one equation and that the part i am not getting...
 
square, and add! :rolleyes:
 

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