1. Not finding help here? Sign up for a free 30min 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!

Moment of inertia

  1. Feb 2, 2008 #1
    [SOLVED] moment of inertia

    1. The problem statement, all variables and given/known data

    what is the moment of interia of these 2 rods (picture attached) about their center of mass
    each rod mass is m with length L

    2. Relevant equations
    one rod i know is [tex]\frac{L^2m}{12}[/tex]


    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Feb 2, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    First things first: Find the center of mass.
     
  4. Feb 2, 2008 #3
    good question

    i thought the answer is [tex]\frac{L^2m}{12}*2+\frac{L^2m}{4}*2[/tex]
    obviously it isnt

    i think center of mass is at [tex]\frac{L}{4}\hat{x}-\frac{L}{4}\hat{y}[/tex]
     
    Last edited: Feb 2, 2008
  5. Feb 2, 2008 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Good--it's right in the middle between the two rod centers. So what's the distance from the center of each rod to that center of mass? To find the rotational inertia of the rods about that center of mass, use the parallel axis theorem.
     
  6. Feb 2, 2008 #5
    yeah i got it it is [tex]\frac{L^2m}{12}*2+\frac{L^2m}{8}*2[/tex] and one more thing if it was a square or rods i would have to multiply by 4?
     
  7. Feb 2, 2008 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Good.
    If it were a square of rods, the distance from each rod to the center of mass would be different. (But there would be a factor of 4 involved.)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Moment of inertia
  1. Moment of Inertia? (Replies: 9)

Loading...