Simple Work On Line Question.

  • Thread starter Master J
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  • #1
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Simple question.

So in an example question I'm lookin at finding the work between 2 points on a line.

The points are A(1, 0, 0) and B(0, 1, (pi^3)/8)

The vector of the line joining these points is then given as:

r = i + t(-i + j + [(pi^3)/8]k )


Is that correct? I can't see how that equation arises? It could just be a typo, or I'm just having a stupid day!!

Cheers!!
 

Answers and Replies

  • #2
jtbell
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No, that's the parametric equation of the (straight) line connecting those points. Taking different values of t in the range [0,1] gives you different points along that line.
 
  • #3
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Yes, but is it correct? Shud there be a -i in there?

Is it r = a + tb ????
 
  • #4
jtbell
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It looks OK to me. Substitute t = 0 and you get point A. Substitute t = 1 and you get point B. In unit vector notation,

[tex]\vec A = 1 \hat i + 0 \hat j + 0 \hat k[/tex]

[tex]\vec B = 0 \hat i + 1 \hat j + \frac{\pi^3}{8} \hat k[/tex]
 
  • #5
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I guess I'm confused as to that vector. How do you make that position vector from those 2 points?
 
  • #6
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The vector from B to A is simply
[tex]\vec{B} - \vec{A}[/tex]
 
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