1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Calculate the moment of inertia of a right triangle

  1. Apr 2, 2009 #1
    1. The problem statement, all variables and given/known data

    A right triangle has height 'h' and width 'b.' The right triangle has a constant area density. Calculate the moment of inertia of the triangle rotated around an axis that runs along side 'h.'

    2. Relevant equations

    I = integral(r^2*dm) where 'r' is distance from the axis

    3. The attempt at a solution

    equation of hypotenuse is (h/b)

    r^2 dm = r^2 * p * dA where p is area density and dA is the area of the rectangles.

    = r^2 * p * (h/b)r * dr = r^3 * p * (h/b) * dr --> integrate =
    ( (ph)/(3b) )r^3 with the limits of integration being from r=0 to r=b so:
    ( (ph)/3 )b^2 - 0 so I = ( (ph)/3 )b^2

    But all my friends said I was wrong so can someone please tell me why?
  2. jcsd
  3. Apr 2, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi homeslice64! Welcome to PF! :smile:

    (have an integral: ∫ and try using the X2 tag just above the Reply box :wink:)
    erm :redface: … ∫r3dr isn't r3/3 :wink:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Calculate the moment of inertia of a right triangle