Results 1 to 2 of 2

Math Help - I need help setting up these equations for using shell method to find volumes.

  1. #1
    Newbie
    Joined
    May 2009
    Posts
    2

    I need help setting up these equations for using shell method to find volumes.

    i am trying to make up my own equations for shell method and completely forgot how to do them. because we did them earlier in the year and have relied mainly on disc method.

    My original function will be y=x^2. i have to include revolving around the x-axis, y-axis, x=a, and y=a and have to use the same example with each method. i have came up with

    y=x^2, y=0, x=2 revolve around y-axis
    y=x^2, y=0, x=2 revolve around x= 3
    x= sqr(y), y=0, x=2 revolve around x-axis
    x= sqr(y), y=0, , x=2 revolve around y= 4

    *integral for first two will be from 0 to 2 and for the last 2 will be from 0 to 4
    *i am not sure if they will even work because i am having to make up my example

    what would be the p(x)h(x) or p(y)h(y) for each of those?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by nuwin View Post
    i am trying to make up my own equations for shell method and completely forgot how to do them. because we did them earlier in the year and have relied mainly on disc method.

    My original function will be y=x^2. i have to include revolving around the x-axis, y-axis, x=a, and y=a and have to use the same example with each method. i have came up with
    see here

    i will use the shell method for all. all integrals will be written in the form: V = 2 \pi \int_a^b (\text{radius})(\text{height})~dx

    y=x^2, y=0, x=2 revolve around y-axis
    V = 2 \pi \int_0^2 (x)(x^2)~dx

    y=x^2, y=0, x=2 revolve around x= 3
    V = 2 \pi \int_0^2 (3 - x)(x^2) ~dx

    x= sqr(y), y=0, x=2 revolve around x-axis
    V = 2 \pi \int_0^4 (y)(2 - \sqrt y) ~dy

    x= sqr(y), y=0, , x=2 revolve around y= 4
    V = 2 \pi \int_0^4 (4 - y)(2 - \sqrt y) ~dy



    be sure that you can identify what i used for the radius when we are not going about either of the axis. in the shell method, there are only 3 forms for the radius, and it does not depend on the function. you can memorize them. (they make sense, so you can figure them out too. so make sure you know them)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 9
    Last Post: January 3rd 2011, 06:22 PM
  2. Cylindrical shell method to find volume
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 16th 2010, 09:08 PM
  3. Volumes Using Shell Method Question
    Posted in the Calculus Forum
    Replies: 1
    Last Post: February 6th 2010, 03:34 PM
  4. Replies: 2
    Last Post: September 30th 2008, 04:16 AM
  5. Replies: 2
    Last Post: August 17th 2008, 12:02 PM

Search Tags


/mathhelpforum @mathhelpforum