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Homework Help: Line integrals and vector fields.

  1. Nov 9, 2011 #1
    1. The problem statement, all variables and given/known data
    There is a circle of equation x^2+y^2=1 and a vector field F (x; y) =< y + .5x, x + .3y >.
    Imagine the field zoomed in extremely close at (0,1), to the point where it looks like a constant field of <-1,.3>. Calculate the work from say (0,1) to (-.001, 1). The constant field is force.

    2. Relevant equations
    I was told to do this I dot <-1,3> and the vector made by (0,1) to (-.001,1).

    3. The attempt at a solution
    I receive an extremely tiny negative number, and I think it is wrong because when going right to left, the value looks like it should be positive. I think I somehow got the vector made by the 2 points wrong, cause I get <1,1.001>.

    Thanks in advance.
  2. jcsd
  3. Nov 10, 2011 #2


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    Science Advisor
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    Gold Member

    The vector from your start point to the second point is D = <-.001,1> - <0,1> = <-.001,0>. Dotting that into your force will yield a positive number.
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