# 3d Equilibrium and moment

1. Oct 18, 2013

### U of T Student

1. The problem statement, all variables and given/known data

in the attached picture are all the information needed to solve the problem.

The bent rod of a negligible weight is supported by a ball and a socket joint at A and a single journal bearing at B. End of D of the rod rests against a friction-less vertical surface. find the reaction forces at A and B.

2. Relevant equations

sum of forces
sum of moments
Reaction forces:
Dx
By
Bx
Mbx
Mby
Ax
Ay
Az

3. The attempt at a solution

moment around a line AB to get D
but then i am stuck!!
should i get the moment around line AD to get By and Bx? or there is even an easier way? double 2D perhaps?
I know i can use the moment around A and the equilibrium of forces in X,Y, and Z
but that will take the whole day, and i am sure the prof created the question in a way that will screw you up if you solve it using the equilibrium equations.

I would be grateful if you help me with this.

#### Attached Files:

• ###### civ100 midterm.png
File size:
32.6 KB
Views:
1,303
2. Oct 19, 2013

### SteamKing

Staff Emeritus
What's wrong with drawing a free body diagram and showing the reactions? With writing the equations of equilibrium and solving them? You seem so fixated on calculating moments about this axis or that axis that you are ignoring the basics. You have also apparently become a little paranoid, thinking your prof has devised some double secret, tricky problem that you'll screw up.

Well, it seems his secret plan is working.