Why Does the Projection of Vector A on B Not Equal Zero?

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Discussion Overview

The discussion revolves around the projection of vector A onto vector B, specifically addressing a scenario where vector A is (1,0) and vector B is (-1,0). Participants explore the implications of the projection result and the conditions under which projections and dot products yield zero.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the projection of A on B results in -1 instead of zero, suggesting a misunderstanding of the concept.
  • Another participant asks about the condition for dot products to be zero, implying a connection to the projection issue.
  • A participant clarifies that the projection is not expected to be zero since the vectors are opposite, indicating that the projection reflects the magnitude in the direction of B.
  • There is a discussion about the meaning of a zero projection, with participants suggesting that it relates to the vectors being perpendicular.
  • One participant asserts that opposite vectors are not perpendicular, as they point in the same direction but are opposite in orientation.

Areas of Agreement / Disagreement

Participants generally agree that the projection of A onto B should not be zero due to the nature of the vectors involved. However, there is some confusion regarding the definitions and implications of projections and dot products, indicating unresolved conceptual differences.

Contextual Notes

There are limitations in the discussion regarding the definitions of projections and dot products, as well as the assumptions about vector orientation and their implications for the projection results.

amaresh92
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greetings,
consider two vector as it is A(1,0) and B(-1,0). now if we find the projection of A on B we should get zero but its coming -1.where i am going wrong?
advanced thanks.
 
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What's the condition for dot products to be zero?
 
Hi amaresh92! :smile:

You're not going wrong.
The projection is not supposed to come out as zero, since the vectors are opposite.

Repeating Ibix, do you know what it means if the projection is zero?
 
I like Serena said:
Hi amaresh92! :smile:
Repeating Ibix, do you know what it means if the projection is zero?

what i have understood is we find projection of one vector to another when we need to find the magnitude of one vector in the direction given by another vector.

if its wrong then what is dot product and projections are ?

any help will be appreciated
thanks
 
Your understanding appears to be correct. Your application to this particular problem is wrong.

Your vector A points due East. Which way is B pointing? How far in an easterly direction is that, ignoring any northerly or southerly motion?
 
The dot product and projection are zero if and only if the vectors are perpendicular.

Opposite vectors are not perpendicular - they are in the same (but opposite) direction.
 

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