What is the significance of \hat{\theta} in polar vector coordinates?

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Discussion Overview

The discussion revolves around the significance of the unit vector \hat{\theta} in polar vector coordinates, particularly in relation to the representation of vectors in polar versus Cartesian coordinates. Participants explore the necessity and implications of using \hat{\theta} alongside \hat{\textbf{r}} in describing vectors.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the necessity of \hat{\theta}, suggesting that a vector described by \textbf{r}=r \hat{\textbf{r}} is complete without it.
  • Another participant challenges this view, arguing that \hat{\textbf{r}} depends on the angle \theta and cannot be defined without it, implying that \hat{\theta} is necessary for a complete description.
  • A participant expresses confusion over the physical meaning of combining \hat{\textbf{r}} and \hat{\theta}, questioning the need for \hat{\theta} in representing vectors.
  • There is a discussion about whether \textbf{r} can be considered a general vector in Cartesian coordinates, with some participants suggesting that the differences between coordinate systems are not clear.
  • One participant seeks clarification on how to visualize the resultant of \hat{\textbf{r}} and \hat{\theta}, indicating a need for a deeper understanding of their relationship in polar coordinates.

Areas of Agreement / Disagreement

Participants express differing views on the role of \hat{\theta} in vector representation. There is no consensus on whether \hat{\theta} is necessary for a complete description of vectors in polar coordinates, and the discussion remains unresolved.

Contextual Notes

Participants have not fully defined their assumptions regarding the completeness of vector descriptions in different coordinate systems, and there are unresolved questions about the physical interpretation of the unit vectors.

ice109
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i don't understand the point of \hat{\theta} if a vector is completely described by \textbf{r}=r \hat{\textbf{r}}

btw tex is doing something weird, apparently i can't make greek letters bold
\textbf{\delta}
 
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no one of you math geniuses can answer this for me?
 
I don't pretend to be a math genius but perhaps none of them understands your question. What do you mean by "a vector is completely described by \textbf{r}=r \hat{\textbf{r}}". Are you talking about a specific vector? Because that certainly does not "completely describe" a general vector. If you have a vector "completely described" by \textbf{r}=r \hat{\textbf{r}} then you don't need \theta'.

If you have formulas for both r' and \theta', what makes you think that the vector is "completely described" by \textbf{r}=r \hat{\textbf{r}}
? Perhaps it would help if you stated the precise problem.
 
\hat{\textbf{r}}[/itex] depends on \theta... It changes according to the angle. Unless you know what \theta is you can't draw \hat{\textbf{r}}[/itex]
 
HallsofIvy said:
I don't pretend to be a math genius but perhaps none of them understands your question. What do you mean by "a vector is completely described by \textbf{r}=r \hat{\textbf{r}}". Are you talking about a specific vector? Because that certainly does not "completely describe" a general vector. If you have a vector "completely described" by \textbf{r}=r \hat{\textbf{r}} then you don't need \theta'.

If you have formulas for both r' and \theta', what makes you think that the vector is "completely described" by \textbf{r}=r \hat{\textbf{r}}
? Perhaps it would help if you stated the precise problem.

does \textbf{r} describe a general vector in cartesian coordinates? if it does then i don't see any difference between the position vector in cartesian coordinates and in polar coordinates.

in fact i don't even understand the physical meaning of a linear combination of \hat{\textbf{r}} and \hat{\theta}. actually that is erroneous , i have no problem visualizing the resultant of these two vectors, i would just need to connect them head to tail. what i don't understand is what i said before, what is the point of the \hat{\theta}}

the picture represents my understanding of the the polar coordinates in terms of the cartesian coordinates where \textbf{A} is the vector I'm trying to describe in terms of the the polar unit vectors. is it correct? and if it is correct why can't describe \textbf{A} by just scaling the \hat{\textbf{r}} a little and making its \theta argument little bigger?
 

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