Magnitude and Direction of Force

AI Thread Summary
To determine the direction and magnitude of force F3, given that the resultant force of three vectors is 20 lb and F3 is the smallest force, the discussion highlights the challenge of having multiple unknowns in the equations. The participants emphasize the need to consider both F3 and the angle θ as unknowns, complicating the calculations due to the presence of sine and cosine functions. A suggestion is made to square and add the forces to simplify the problem. The conversation reflects a struggle with the mathematical approach but encourages collaboration for a solution. Ultimately, the focus remains on resolving the equations to find F3 and its direction.
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?
 
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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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