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!

What is the moment of inertia of the object about an axis at the left end of the rod?

  1. Mar 2, 2013 #1
    1. The problem statement, all variables and given/known data

    An object is formed by attaching a uniform, thin rod with a mass of mr = 6.91 kg and length L = 4.88 m to a uniform sphere with mass ms = 34.55 kg and radius R = 1.22 m. Note ms = 5mr and L = 4R.

    What is the moment of inertia of the object about an axis at the left end of the rod?

    attachment.php?attachmentid=56284&stc=1&d=1362266421.png

    2. Relevant equations
    I came up with these equations...
    I_rod = (1/3) * mr * L^2
    I_sphere = (2/5) * ms * R^2 + ms * (L + R)

    3. The attempt at a solution

    I think that the moment of inertia for the system is equal to the sum of I_rod and I_sphere. So I simply plugged in the relevant variables and got the answer of 286.177 kg-m^2 which is wrong. Are the equations above correct?
     

    Attached Files:

  2. jcsd
  3. Mar 2, 2013 #2

    Doc Al

    User Avatar

    Staff: Mentor

    That second term, from the parallel axis theorem, should have the distance squared.
     
  4. Mar 2, 2013 #3
    Thanks. That was stupid of me. I did the problem twice and made the same mistake twice.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What is the moment of inertia of the object about an axis at the left end of the rod?
Loading...