Statics: parallel forces problem

AI Thread Summary
The discussion revolves around solving a statics problem involving parallel forces and determining the coordinates of the resultant force. The initial calculations led to a resultant force of R = 0i + 0j -125 k and a moment vector M = -30 i + 110 j. The user encountered an error in their solution, specifically in the assignment of x and y coordinates. After switching the values of x and y, the correct coordinates were found to be x = 0.24 and y = 0.88. The confusion stemmed from the initial misalignment of the coordinates in the cross product equation.
c1tonsoup
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Homework Statement



Determine the x- and y-coordinates of a point through which the resultant of the parallel forces passes.

The Attempt at a Solution


The first thing I did was to find the resultant forces, which is R = 0i + 0j -125 k
Then I found the moment of each axis
so
M = (-65(12) -65(6) +60(12) +35(12) ) i + (-65(11)-35(15)+90(15))j + 0k
M = -30 i + 110 j

Then the next thing I did is
r x R = M
so
(xi + yj + zk) x (-125 k) = (-30 i +110 j)
-125y i + 125x j = -30 i + 110 j
so x and y I got is
x= 0.24
y = 0.88

why is it wrong?
Thanks for the help
 

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Did you switch x and y ?
 
BvU said:
Did you switch x and y ?
Haha I just did and got the right answer. But i don't understand why that's the case. i did all my math right
 
c1tonsoup said:
-125y i + 125x j = -30 i + 110 j
Says y = 30/125 and x = 110/125 !
 
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