Understanding converting a vector field to cartesian coords

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Homework Help Overview

The discussion revolves around converting a vector field to Cartesian coordinates, specifically focusing on a problem that includes a part that participants find confusing. The original poster expresses uncertainty about the reasoning behind the solution provided for part B and questions the origin of a specific angle used in the calculations.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the reasoning behind the steps taken in the solution, particularly regarding the use of angles and vector components. There are inquiries about the interpretation of terms and the application of equations related to Cartesian coordinates.

Discussion Status

The conversation is ongoing, with participants seeking clarification on specific aspects of the problem. Some guidance has been offered regarding the interpretation of angles and vector components, but there is no explicit consensus on the overall understanding of part B.

Contextual Notes

Participants are working with a problem that involves converting vector fields and are referencing specific angles and components that may not be fully explained in the original problem statement. There is an indication that certain assumptions or equations may be critical to understanding the solution.

shemer77
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Homework Statement


Here is the problem and solution but I am confused as to part B
http://gyazo.com/e77d05fc67cb6ac266ff021ef88052dc


The Attempt at a Solution


I understand the first part, but I am totally lost on how they reached their cartesian answer for part B. Firstly why did they do what they did, and secondly where did 36 degrees come from?

I feel like their is some sort of equation or something I am not understanding.
 
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shemer77 said:

Homework Statement


Here is the problem and solution but I am confused as to part B
http://gyazo.com/e77d05fc67cb6ac266ff021ef88052dc

The Attempt at a Solution


I understand the first part, but I am totally lost on how they reached their cartesian answer for part B. Firstly why did they do what they did, and secondly where did 36 degrees come from?

I feel like their is some sort of equation or something I am not understanding.

36 degrees is 0.2π. It's the angle the gave you for phi. Does that help? Other than that they are just using that if u is a unit vector then the component of D along u is (D.u)u.
 
Hmm ok but why does he have .5 twice as in .5(ap.ax)ax +.5(ap.ax)ay?
 
shemer77 said:
Hmm ok but why does he have .5 twice as in .5(ap.ax)ax +.5(ap.ax)ay?

One term finds the ax component of 0.5ap and the other finds the ay. Are you sure you understood the first part?
 
hmm okay thanks I think I figured it out. All I did was use the equations x = p*cosphi, y=p*sinphi and plugged those into the original equation which was already in cartesian for me.
 

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