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Homework Help: Volume of Solid of Revolution Question

  1. Jul 17, 2011 #1
    1. The problem statement, all variables and given/known data

    y= -(x/6) + b, find the volume as this solid is rotated 360 degrees around the Y axis


    2. Relevant equations

    If I were given the interval at which I needed to find the volume and/or the value of B I could easily do this using the formula:

    [pi] Integrate: (R(y))2 dx


    3. The attempt at a solution

    What I am trying to ascertain is whether or not this problem is even doable. I dont know if my professor intentionally left out the interval and b value and wants us to do it algebraically but I can't move ahead as most of the questions are based off this one. Please help!
     
  2. jcsd
  3. Jul 17, 2011 #2

    hunt_mat

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    The general formula for this is given by:
    [tex]
    V=\pi\int_{a}^{b}y^{2}(x)dx
    [/tex]
     
  4. Jul 17, 2011 #3
    is it possible to do this question without being given the bounds or knowing where the line sits? Because there is no y intercept and I'm not too sure how you would find the volume without enough information to get the area of the original shape
     
  5. Jul 17, 2011 #4

    tiny-tim

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    welcome to pf!

    hi reybob! welcome to pf! :smile:
    no, without limits it makes no sense :redface:
     
  6. Jul 17, 2011 #5

    LCKurtz

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    Gold Member

    Of course, you mean dy.

    You could make up your own x or y limits of c and d and leave your answer as a function of c, d, and b. Better might be to ask the prof if he forgot to include limits.
     
  7. Jul 17, 2011 #6
    Yeah I think I'm going to have to do that. Thank you so much for all this help, this forum rocks!
     
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