Statics: parallel forces problem

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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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  • Diagram of a bent L-shaped plate in 3D axes with forces applied: 65 lb at top left, 65 lb on the front face, 60 lb along the top edge, 35 lb at the right top, and 90 lb at the bottom right. Dimensions marked 11 in, 15 in, 6 in, 12 in and 15 in.
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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 !