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Problem involves 2 unknown forces 
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#1
Sep2513, 05:09 PM

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Suppose that a problem involves 2 unknown forces at certain specified points (point forces), along with other relevant info that leads to having 2 equations to solve for the unknown variables.
Assuming that the force at one point is solved for easily...that the forces are perpendicular to one another so that Summing the forces in only 1 direction provides the answer for the previously unknown force...call it force "X" at point "A" Is it acceptable to then Sum the moments at "A" or should I use any point other than "A" ? Thanks in advance 


#2
Sep2513, 09:46 PM

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I am not sure what you mean by "2 unknown forces at certain specified points" ....an example or picture would help....but in any case, if the object is in equilibrium, you can sum moments about any point you want, but usually you should pick the best point to make your solution easier to obtain. If you have solved, for example, the xcomponent of the force at A, and you are looking for the ycomponent of the force at A, you should pick another point instead of A about which to sum moments, because summing moments about A will not directly give you the answer for that ycomponent at A. You should provide a sample problem for clarification of your question.



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