Results 1 to 5 of 5
Like Tree1Thanks
  • 1 Post By tom@ballooncalculus

Math Help - Finding volume by using washer method and shell method

  1. #1
    Newbie
    Joined
    Sep 2013
    From
    United States
    Posts
    4

    Finding volume by using washer method and shell method

    Find the volume of the solid generated by revolving the region bounded by y=2x, y=0, x=2, and x=4, around the y - axis.

    I am having trouble getting the same answer using both the washer method and the shell method. For the washer method I get π(112/3), and with the shell method I get 2π(112/3). I can not figure out if I am doing one of them, or both of them wrong.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Apr 2005
    Posts
    14,973
    Thanks
    1121

    Re: Finding volume by using washer method and shell method

    You don't say HOW you got those answers so I don't see how anyone can tell what you might have done wrong.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Sep 2013
    From
    United States
    Posts
    4

    Re: Finding volume by using washer method and shell method

    I meant to upload two photos, I will do that now, thanks
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Sep 2013
    From
    United States
    Posts
    4

    Re: Finding volume by using washer method and shell method

    Finding volume by using washer method and shell method-photomath.jpg
    Finding volume by using washer method and shell method-photo2.jpg
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    Joined
    Oct 2008
    Posts
    1,034
    Thanks
    49

    Re: Finding volume by using washer method and shell method

    The shells working is correct. For the washers, if you subtract one integral from another then that wants to be subtracting the integration of smaller discs (green here),



    from that of the larger. You can do the subtraction inside the integral (integrate all the washers, each one a blue minus green), but you do need a separate integral from 0 to 4 and from 4 to 8.
    Thanks from garage24
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Washer and Shell Method (Newbie)
    Posted in the Calculus Forum
    Replies: 1
    Last Post: April 12th 2013, 06:52 AM
  2. Replies: 3
    Last Post: June 24th 2012, 11:31 AM
  3. Replies: 2
    Last Post: April 19th 2009, 09:50 AM
  4. finding volume by the washer method
    Posted in the Calculus Forum
    Replies: 2
    Last Post: April 12th 2009, 04:43 PM
  5. Replies: 0
    Last Post: February 24th 2009, 01:06 AM

Search Tags


/mathhelpforum @mathhelpforum