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Engineering Mechanics Couple system question

by Taiki_Kazuma
Tags: couple, engineering, mechanics
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Taiki_Kazuma
#1
May26-05, 09:16 PM
P: 23
what is this problem searching for?

A 25-lb force acting in a vertical plane parallel to the yz plane is applied to the 8-in.-long horizontal handle AB of a socket wrench. Replace the force with an equivalent force-couple system at the origin O of the coordinate system.


See attached pic of the problem.

AO is 15-in.-long vertical

AB is 30 degrees off the x-axis

Force(in red) is 25-lb and is 20 degrees from the -z-axis

-------------------------------------------------------------

ok tell me if I"m wrong.

I think this problem is looking for the force that should be applied to cancel the other force but still have the same moment about O.

Please tell me if I'm thinking correctly...

however, how should I go about doing that? if that is the solution to this problem.
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FredGarvin
#2
May27-05, 06:51 AM
Sci Advisor
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P: 5,095
Quote Quote by Taiki_Kazuma
A 25-lb force acting in a vertical plane parallel to the yz plane is applied to the 8-in.-long horizontal handle AB of a socket wrench. Replace the force with an equivalent force-couple system at the origin O of the coordinate system.

I think this problem is looking for the force that should be applied to cancel the other force but still have the same moment about O.
Not exactly. What you need to do is come up with a force and moment that, when applied at the point O, are equivilent to the lone force acting at the end of the handle.
Taiki_Kazuma
#3
May27-05, 12:45 PM
P: 23
ok, I think I get it.....please correct me if I'm wrong (and let me know if I'm right)...


First I add vectors that are equal to F and -F at point O.

then I find the couple produced by F (original force) and -F. That will give me the answer of the couple moment at point O. and then I have F applied at O left over.

Is that what it is looking for?

I calculated the following answers:

M = 196.94i + 352.35j - 128.25k

F = -8.55j + 23.49k

Pyrrhus
#4
May27-05, 11:38 PM
HW Helper
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P: 2,278
Engineering Mechanics Couple system question

Taiki, you only need to calculate the moment of F with respect to the origin, and put the rectangular representation of F. That should give you your Force-couple system at O.


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