cowboys647

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!

y8s

iTrader: (8)

what are you solving for? Ay?

who says you need 3 equations?

cowboys647

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

cowboys647

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

cowboys647

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...????

DaveC

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.

TorqueZombie

iTrader: (6)

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

Staffah

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.

Efini~FC3S

iTrader: (4)

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...

cowboys647

Sweet figured it out, thanks guys!