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How negative sign appeared out of nowhere?

  • #1

Homework Statement:

Determine the required magnitude of force F in the resultant couple
moment on the frame is 200 lb.ft clockwise.

Homework Equations:

##\Sigma F_x = \textbf{-}2*\frac{4F}{5}##
I have to find resultant for this couples:

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My sir resolved given forces into components like this:

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He considered Fx couples for sides 3,4,5 triangles:

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He wrote resultant force for this above diagram: ##\Sigma F_x = \textbf{-}2*\frac{4F}{5}##
 

Answers and Replies

  • #2
haruspex
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You appear to have written the vertical component as 4/3 F, twice, instead of 4/5, and the horizontal once as 4/3 instead of 3/5.

Which point are you taking moments about?
 

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