Statics: parallel forces problem

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Discussion Overview

The discussion revolves around a statics problem involving the determination of the x- and y-coordinates of a point through which the resultant of parallel forces passes. Participants are analyzing the calculations related to resultant forces and moments.

Discussion Character

  • Homework-related

Main Points Raised

  • One participant presents their calculations for the resultant forces and moments, leading to a proposed solution for the coordinates x and y.
  • Another participant questions whether the x and y values were switched in the calculations.
  • A later reply confirms that switching x and y led to the correct answer, but expresses confusion about why this was necessary despite the initial math appearing correct.
  • Another participant interprets the equation involving the resultant forces and moments, suggesting specific values for y and x based on the equation provided.

Areas of Agreement / Disagreement

There is no consensus on the correctness of the initial calculations, as participants are debating the switching of x and y values and the implications of that switch.

Contextual Notes

Participants have not fully resolved the reasoning behind the necessity of switching x and y, and there may be assumptions or definitions related to the coordinate system that are not explicitly stated.

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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