Solving a 3D Statics Problem: Identifying Unknown Angles in a Free Body Diagram

[VitaX]

Homework Statement

[PLAIN]http://img846.imageshack.us/img846/6546/statics.png

Homework Equations

Fy = F*cosθy
Fh = F*sinθy

Fx = Fh*cosφ = F*sinθy*cosφ
Fz = Fh*sinφ = F*sinθy*sinφ

The Attempt at a Solution

I'm having a lot of trouble drawing vector AD in a free body diagram. I think I need to draw one as that will help me further understand the solution that is worked out. I'm just having trouble identifying the angles that I should utilize and where on the diagram they should be placed. If someone could possibly draw up a diagram that helps with identifying what is what that would be very helpful.

Fy = F*cos30
Fh = F*sin30

You could say my main problem is identifying which is φ, I just cannot tell from the picture at all. What exactly is φ defined as, my book's definition is pretty vague.

Or am I going about this the wrong way?

 

[tiny-tim]

Hi VitaX!

Fx = Fh*cosφ = F*sinθy*cosφ
Fz = Fh*sinφ = F*sinθy*sinφ

φ is the angle from the x-axis (in the x,z plane)

since the tension has to be along AD,

the easiest way to do this is to use O as the origin and to find the (x,y,z) coordinates of A and D …

then the vector (D - A) is the one you want, and you can find the angles by "dotting" it with each of the three unit vectors along the axes ​

 

[VitaX]

Hi VitaX!


φ is the angle from the x-axis (in the x,z plane)

since the tension has to be along AD,

the easiest way to do this is to use O as the origin and to find the (x,y,z) coordinates of A and D …

then the vector (D - A) is the one you want, and you can find the angles by "dotting" it with each of the three unit vectors along the axes ​

Ok thanks for that, determined it to be 40 degrees. Was finally able to get a good drawing of it.