3D statics - looks impossible to solve

[Femme_physics]

This question was on my mechanics test but I skipped it. It seemed kinda crazy.

Homework Statement

In the drawing is described a weightless beam AC connected to the wall through joint C. The beam is supported by two cables, BE and AD, connected to the wall. At the end of the beam at point A, acts a vertical force of 880 [N]


A) Calculate the tension in cables AD and BE

B) Calculate reaction at joint C

http://img685.imageshack.us/img685/3816/birdplane.jpg

The Attempt at a Solution

I'll spare you the rest of the equations, since no matter what view I'm looking at ...too many unknowns at sigma torque equation!

http://img16.imageshack.us/img16/5538/try3d1.jpg

http://img23.imageshack.us/img23/244/try3d2.jpg

 

[I like Serena]

What happened to the sum of forces equations?

 

[Femme_physics]

That would just end up adding another unknown, Ay! So I'd end up with 3 unknowns. At least here I got 2 unknowns!

 

[Femme_physics]

Can you admit at least this is the most difficult 3D problem we've encountered yet?

Also, how'd you get 200+ posts more than me?!?? I've been slacking!

 

[I like Serena]

Still, writing up all equations will get you your answer.
Whereas getting stuck at more unknowns than equations, will not get you your answer. ;)

How many equations do you think you can get?
And which unknowns do you think you would have?

 

[I like Serena]

Can you admit at least this is the most difficult 3D problem we've encountered yet?

Hmm, I don't think so.

Also, how'd you get 200+ posts more than me?!?? I've been slacking!

Well, I've been posting more in GD than you have...

 

[Femme_physics]

Added it

http://img827.imageshack.us/img827/9606/fxfy.jpg

Tad, Tbe, Cx and Cy are unknown.

3 equations
4 unknowns

cannot be solved, right?

 

[I like Serena]

You should have 6 equations...

 

[Femme_physics]

You should have 6 equations...

6 equations! and you're telling me this is NOT the hardest problem we've done??

 

[Femme_physics]

In ALL other 3D statics problems, we were able to take just one view, do one moment equations, and find one unknown, and then from that point on it was a smooth ride. There were NEVER systems of equations!

I hope I don't appear lazy! I just want to gauge the craziness of this question before carrying on to actually solve it

 

[I like Serena]

Well, you had a number of other problems where you needed 3 views.
And often you did not write out all the equations, although you did use them.
It's just that you already saw beforehand which way to go and getting a smooth ride.

In statics I believe you did not have to solve systems of equations yet, as opposed to electronics.
Perhaps in this one you do have to solve a system of equations.
But you're good at that now, after all the exercises in electronics!

 

[Femme_physics]

Actually I solved many statics problems with 3 equations 3 unknowns! I just didn't post them here because they were easy

But none of them were 3D!

Well, you had a number of other problems where you needed 3 views.
And often you did not write out all the equations, although you did use them.
It's just that you already saw beforehand which way to go and getting a smooth ride.

In all other problems, 1 equation was enough to start with. In here, you start with 6! Definitely harder, but still, seemingly solvable. I just wanted to see the direction, I'll have to do the final blow another time...^^ Thanks