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Old 07-29-2013, 05:07 PM   #1
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Default Statics Problem Help!

Hey guys I'm having a bit of trouble on this prob. Sorry for the crappy paint pic I made.. If I can find the reactions this prob is easy, just trying to find internal forces. I need three independent equations but all I have is the sum of the forces in the y direction and moments at any point. Just taking another moment equation at another point is just canceling itself out. Help!
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Old 07-29-2013, 05:39 PM   #2
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what are you solving for? Ay?

who says you need 3 equations?
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Old 07-29-2013, 05:44 PM   #3
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I guess I could have labeled better.. I'm trying to find Ay, By, and Dy. Since I have three unknowns, I believe I need three separate equations to solve
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Old 07-29-2013, 05:45 PM   #4
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I should have taken this first..
Alright taking a section from A to E and taking the moment at e gets me a value of 225N for Ay so the shear force at E should also be 225N but the answer in the back of the book is 215N. Sooooo confused
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Old 07-29-2013, 06:59 PM   #5
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Also if I take Ve to be 215N like the back of the book then my DCx force would be 1330N which would mean my Ax would be the same. So then my section from A to E should have an internal normal force of 1330N but its 470N in the back of the book...????
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Old 07-29-2013, 08:52 PM   #6
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It looks like you can write down 2 equations for each of the two sections, making 4 equations total. The extra unkown is Cy which will be equal and opposite for the two sections.
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Old 07-30-2013, 02:18 AM   #7
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If your book is anything like mine have been so far it might be wrong. I've been a large amount of time chasing my tail trying to "get it" and come to find out the book was wrong.

But usually I'm wrong
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Old 07-30-2013, 11:00 AM   #8
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Do a formula for each point under the beam and make the equations equal zero. For example the moment at point a = 0 = fb(4.5) + fd (10) - 25 ..... Doing this you will get three equations. You have to assume that either clockwise or counterclockwise rotation is positive.
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Old 07-30-2013, 05:50 PM   #9
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Quote:
Originally Posted by TorqueZombie View Post
If your book is anything like mine have been so far it might be wrong. I've been a large amount of time chasing my tail trying to "get it" and come to find out the book was wrong.

But usually I'm wrong
Agreed.

My statics and mechanics text books had like 10% of the answers in the back wrong or typos.

Usually our professor would tell us that, after the fact...
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Old 07-30-2013, 08:12 PM   #10
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Sweet figured it out, thanks guys!
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