Results 1 to 2 of 2

Math Help - find the moment of inertia

  1. #1
    Senior Member
    Joined
    Jan 2007
    Posts
    477

    find the moment of inertia

    heres a very messy drawing for an idea of what were looking at: http://img89.imageshack.us/img89/1764/untitledyi0.png

    area moment of inertia Ix0 of a rectangle about the axis x0 that passes through the centroid is: Ix = 1/12bh^3

    the moment of inertia about an axis x that is parallel to the x0 is given by: Ix = Ix0 + Ad^2x

    where A is the area of the rectangle, and dx is the distance between the two axes.

    the inputs are width w, height h, and thickness t.

    w = 200mm h = 300 mm, and t = 22mm

    find the moment of inertia:

    i know i need to use:

    Ix0 = 1/12bh^3

    Ix = Ix0 + Ad^2x


    i've tried to put this together, but i need some help.


    my questions are..

    is t the what plugs into b in this problem?

    also, is area of the rectangle just Base * height, so 200 * 300?

    not sure how to find the distance between the two axis.

    please help.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Global Moderator

    Joined
    Nov 2005
    From
    New York City
    Posts
    10,616
    Thanks
    9
    The distance between the axis is the vertical (or horizontal) distance between the centroid of the figure to the origin.
    Now, the sign over here does not matter because anyway you are squaring.

    But in general when it is important (like in product or inertia) you look if it is to right or left to determine the sign. Similarly when you do this with up and down.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Moment of Inertia
    Posted in the Calculus Forum
    Replies: 18
    Last Post: December 19th 2011, 11:00 AM
  2. Moment of inertia
    Posted in the Calculus Forum
    Replies: 1
    Last Post: July 19th 2009, 03:38 PM
  3. Moment of inertia
    Posted in the Math Topics Forum
    Replies: 0
    Last Post: March 30th 2009, 08:39 PM
  4. moment of inertia
    Posted in the Geometry Forum
    Replies: 0
    Last Post: March 29th 2009, 10:33 PM
  5. find moment of inertia of circular cone
    Posted in the Calculus Forum
    Replies: 2
    Last Post: April 20th 2008, 04:44 AM

Search Tags


/mathhelpforum @mathhelpforum