What's the Difference Between a Position and a Position Vector?

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Discussion Overview

The discussion centers around the distinction between a position and a position vector, particularly in the context of Cartesian coordinates and Euclidean space. Participants explore definitions, implications, and the conceptual framework surrounding these terms, touching on both theoretical and practical aspects.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that a position in a 2D Cartesian coordinate system is absolute and described by two numbers, while a position vector is relative to a starting point, which may or may not be the origin.
  • One participant suggests that a position vector can be viewed as an equivalence class of pairs of points in the plane that satisfy certain conditions.
  • Another participant describes a position in a plane as a coordinate pair (x,y) and a position vector as the vector from the origin (0,0) to that point.
  • Some express skepticism about the concept of a position vector, particularly in non-Euclidean contexts, questioning how it applies to surfaces like spheres.
  • It is noted that in Euclidean geometry, a position may be defined without numerical coordinates, such as through the intersection of lines or the center of a circle, which does not involve a position vector.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the definitions and implications of position versus position vector, with multiple competing views and interpretations remaining throughout the discussion.

Contextual Notes

Some limitations include the dependence on definitions of space and the context in which these terms are used, particularly regarding Euclidean versus non-Euclidean geometries.

san203
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What is a position vector? Is their any difference between the position vector and position? Isnt position of a point supposed to represent its direction in Cartesian plane as well(Positive quadrants , negative quadrants). So why two different terms?
 
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Just at a guess, I'd say it's like this: position in a 2D Cartesian coordinate system is absolute and is described by two numbers. A position vector is relative to some starting point, which MIGHT be the origin but might not be.
 
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One might say that a position vector ##[x\,\,y]## is the equivalence class of pairs of points ##(a,b)##, ##(c,d)## in the plane satisfying ##c-a = x## and ##d-b = y##.
 
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san203 said:
What is a position vector? Is their any difference between the position vector and position? Isnt position of a point supposed to represent its direction in Cartesian plane as well(Positive quadrants , negative quadrants). So why two different terms?

Position in a plane: (x,y)
Position vector in a plane: vector from (0,0) to (x,y)
 
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phinds said:
Just at a guess, I'd say it's like this: position in a 2D Cartesian coordinate system is absolute and is described by two numbers. A position vector is relative to some starting point, which MIGHT be the origin but might not be.

mathman said:
Position in a plane: (x,y)
Position vector in a plane: vector from (0,0) to (x,y)
But isn't position in plane also calculated relative to origin?

jbunniii said:
One might say that a position vector ##[x\,\,y]## is the equivalence class of pairs of points ##(a,b)##, ##(c,d)## in the plane satisfying ##c-a = x## and ##d-b = y##.
Sorry. I didnt understand that at all.

Edit#2 : Thanks. Your answers were right i guess.
 
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Personally, I don't like the very concept of a "position vector"- it only makes sense in Euclidean space. When I was young and foolish (I'm not young any more) I worried a great deal about what a "position vector" looked like on a sphere. Did it "curve" around the surface of the sphere or did it go through the sphere? The answer, of course, is that the only true vectors are tangent vectors that lie in the tangent plane to the surface at each point.
 
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HallsofIvy said:
Personally, I don't like the very concept of a "position vector"- it only makes sense in Euclidean space. When I was young and foolish (I'm not young any more) I worried a great deal about what a "position vector" looked like on a sphere. Did it "curve" around the surface of the sphere or did it go through the sphere? The answer, of course, is that the only true vectors are tangent vectors that lie in the tangent plane to the surface at each point.

This really went over my head, but when i do learn things like this i'll try to keep what you said in mind.
 
A position vector is a vector in Euclidean space that points from the origin to your location
 
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I would say that the biggest difference is that a position vector assumes you are working in a space with numbers (like a Vector Space) and a position may not.

If you are studying Euclidean Geometry, based on the Elements, there are no numbers (at least for many books there is no need of numbers). So a position might be described as the intersection of two lines, or the center of a circle. In this case, there is no position vector, only a position. You are working in a Euclidean space that does not have the usual Vector Space information available.
 

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