Finding a Unit Vector Along $\vec{A}$ - Please Help!

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Discussion Overview

The discussion revolves around finding a unit vector along a given vector $\vec{A}=2\hat{a_{\rho}}-z\hat{a_{z}}$ in cylindrical coordinates. Participants explore whether it is necessary to convert the vector to Cartesian coordinates or if a direct method can be applied to find the unit vector.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant asks how to find a unit vector along the direction of $\vec{A}$ and whether conversion to Cartesian coordinates is necessary.
  • Another participant suggests that the unit vector can be found by dividing the vector by its magnitude, providing a formula for the unit vector in cylindrical coordinates.
  • A subsequent reply questions the validity of obtaining a unit vector directly from the cylindrical form, prompting a discussion about the properties of cylindrical coordinates.
  • Some participants assert that it is valid to find the unit vector directly in cylindrical coordinates, citing that cylindrical coordinates form an orthonormal system and that the length of the vector remains unchanged from Cartesian coordinates.
  • There is a query about whether the same reasoning applies to spherical coordinates, with a request for proof regarding the orthonormality of spherical coordinates.

Areas of Agreement / Disagreement

Participants generally agree that it is valid to find the unit vector directly in cylindrical coordinates, but there is ongoing debate about the applicability of this reasoning to spherical coordinates, which remains unresolved.

Contextual Notes

The discussion includes assumptions about the properties of coordinate systems and their implications for vector magnitudes, but these assumptions are not universally accepted or proven within the thread.

Drain Brain
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Hello! I need help with this problem

how do you find a unit vector along the direction $\vec{A}=2\hat{a_{\rho}}-z\hat{a_{z}}$(cylindrical)?

do I have to convert it to Cartesian or there is a direct method? please help! Thanks!
 
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The vector itself is responsible for the direction. All you need to do is divide the vector by its magnitude:

$$\vec{u} = \frac{\vec{A}}{\| \vec{A}\|} = \frac{2 \vec{a}_{\rho} - z \vec{a}_z}{\sqrt{4+z^2}}.$$
 
Fantini said:
The vector itself is responsible for the direction. All you need to do is divide the vector by its magnitude:

$$\vec{u} = \frac{\vec{A}}{\| \vec{A}\|} = \frac{2 \vec{a}_{\rho} - z \vec{a}_z}{\sqrt{4+z^2}}.$$
HI fantini
$\vec{A}=2\hat{a_{\rho}}-z\hat{a_{z}}$ <--- this vector is in cylindrical form. Why did you directly get the unit vector from a cylindrical form? Is that valid?
 
Yes, it is valid. This is because cylindrical coordinates form an ortonormal system. Thus the length of the vector does not change from cartesian. You can compute the length as you would normally. :)
 
Fantini said:
Yes, it is valid. This is because cylindrical coordinates form an ortonormal system. Thus the length of the vector does not change from cartesian. You can compute the length as you would normally. :)

does this also holds for spherical form?
 
Drain Brain said:
does this also holds for spherical form?

Can you prove if spherical co-ordinates form an orthonormal system?
 

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