Understanding 3D Diagrams for Solving Angle Problems

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lc99
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Homework Statement


3D pipe diagram with a yellow elbow pipe along the z axis and a pipe running along the x axis. A yellow wrench-like handle at the top has labels -F4 = [-150 k] N pointing down, F4 = [150 k] N pointing up, 0.3 m, 0.2 m, 0.2 m and a 30 degree angle.


Homework Equations

The Attempt at a Solution


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I am having trouble visualizing the 30 degree angle? How would i know that it is in between 2 planes and not just 1 plane. I thought it would be in the x/y plane. In cases like this where they should you the angle (arrow) to where a object is turning confuses me. I need help figuring out the direction of these angles.

The answer key has it this way: Which was unlikely what i would visualize it...
Hand-drawn 3D vector diagram with z axis vertical; vectors labeled r_AB, r_AC and r_AB,z, with a 30 degree angle marked between a diagonal line and a dashed projection, labeled (III).
 
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  • 3D pipe diagram with a yellow elbow pipe along the z axis and a pipe running along the x axis. A yellow wrench-like handle at the top has labels -F4 = [-150 k] N pointing down, F4 = [150 k] N pointing up, 0.3 m, 0.2 m, 0.2 m and a 30 degree angle.
    upload_2018-3-27_0-17-15.png
    34.1 KB · Views: 881
  • Hand-drawn 3D vector diagram with z axis vertical; vectors labeled r_AB, r_AC and r_AB,z, with a 30 degree angle marked between a diagonal line and a dashed projection, labeled (III).
    upload_2018-3-27_0-18-51.png
    21.4 KB · Views: 536
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Discussion

SInce there is only one angle given, 30°, it must be a two-dimensional orientation. If it involved three dimensions, an additional angle would have to be specified,

p.s. I agree the visual depiction is confusing, poorly drawn.
 
Since the handle rotates in a plane parallel to the x-z plane, it seems pretty obvious to me that the angle is relative to the plane of rotation of the handle. The handle's position is 30° clockwise from horizontal. The drawing wouldn't make any sense if the angle were interpreted as being a horizontal angle. IMO the only thing wrong with the drawing is that the horizontal ray that indicates the angle measure isn't quite parallel to the x-axis. Other than that, the drawing seems pretty clear to me.
 
The original 3D drawing seems easy enough to interpret. The answer key sketch seems harder. I suspect the problem is with the answer key or your interpretation of it.

Perhaps post the whole problem as written?
 
Mark44 said:
IMO the only thing wrong with the drawing is that the horizontal ray that indicates the angle measure isn't quite parallel to the x-axis
Optical illusion.