Are my answers correct? (3D statics)

[Femme_physics]

I don't have the solution manual answer for this problem, can anyone help please confirm my answers are correct?

Homework Statement

http://img860.imageshack.us/img860/6118/40893341.jpg [/QUOTE]

On a smooth horizontal weightless surface ABDC acts at the center a vertical force of 600 [N]. The surface is connected to the wall through axes A and B and supported by shaft CE.

A) Calculate reaction at CE
B) Calculate reactions at axes A and B. Presume the forces at the B axis are at the X and Y direction only.

The Attempt at a Solution

This is my solution attempt

http://img204.imageshack.us/img204/2712/20112011a.jpg

http://img834.imageshack.us/img834/6539/20112011b.jpg ]


And here below in the thumbnail I have attached my friend's attempt. He's smart, but new to 3D statics, and I don't understand how what he did makes sense. In fact it contradicts my results and methods.

 

[I like Serena]

This is my solution attempt

http://img204.imageshack.us/img204/2712/20112011a.jpg

I don't understand what your friend did.
It looks rather complex, but his answers are wrong.

I definitely prefer your method.
Reducing the problem to 2D makes it much easier to follow what you did.

However, you also made a mistake.
It starts with your zx-view, when you calculated TCE_zx where you used TCE_y, but you should have used TCE_x.
Same for the calculation of TCE_z.

As a consequence, your B_x, A_x, and A_z are wrong too.

 

[Femme_physics]

However, you also made a mistake.
It starts with your zx-view, when you calculated TCEzx where you used TCEy, but you should have used TCEx.
Same for the calculation of TCEz.

As a consequence, your Bx, Ax, and Az are wrong too.

*smacks forehead*

I'll tell you why, I'm used to "y" being up so I keep confusing myself :tongue:


Thanks a bunch will correct it today

 

[I like Serena]

I'll tell you why, I'm used to "y" being up so I keep confusing myself :tongue:

But "y" is up! :tongue2:

 

[Femme_physics]

But "y" is up! :tongue2:

It's "up" in the 3D drawing. But in the 2D ones, it's always psychologically my "up"-- something which I still haven't completely gotten rid off.

 

[I like Serena]

It's "up" in the 3D drawing. But in the 2D ones, it's always psychologically my "up"-- something which I still haven't completely gotten rid off.

Uhh, it's up in 3D and it's up in your yx-view and it's up in your yz-view. :uhh:

It's just that in 3D normally z is always up, and in the yz-view z should be up too!

 

[Femme_physics]

Yes, I said psychologically "up" as in the sense that's it's pointing towards the upper part of the page that I'm writing on heh, I still haven't gotten over it is what am saying

 

[I like Serena]

Still, in this problem y is pointing up to the physical top of your page.

I think you've gotten over that just fine!
You're already used to the fact that z should be pointing up to the physical top of your page.

The challenge in this problem is to apply the direction of the y-coordinate mathematically, carefully without making assumptions based on the 3D you're already used to.
That really makes this problem harder than it has to be.

 

[Femme_physics]

Still, in this problem y is pointing up to the physical top of your page.

not if you're looking at the xz view

 

[I like Serena]

not if you're looking at the xz view

*smacks forehead*

Oooooooooooooooooooooooh!
(Thanks for clarifying that! )

 

[Femme_physics]

*grins* anytime!

The correction

http://img814.imageshack.us/img814/3315/final1k.jpg

http://img543.imageshack.us/img543/6226/final2x.jpg

http://img215.imageshack.us/img215/8088/final3a.jpg

 

[I like Serena]

Yay!

You didn't ask for it, but I give it the ILSe-stamp-of-approval.
Btw, whatever happened to that item that I didn't put a stamp-of-approval on?

 

[Femme_physics]

Maybe I didn't ask, but I secretly desired!
Thanks :mrgreen:

"Btw, whatever happened to that item that I didn't put a stamp-of-approval on?
"

To be amended, rest be assured!