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!

Homework Help: Parallel-axis theorem

  1. Nov 25, 2007 #1
    1. The problem statement, all variables and given/known data
    If I have a solid sphere (I = (2/5)MR^2) and it rotates around a point on an axis that is 5m away (it has radius 0.1m) - is the moment of inertia then: I = (2/5)MR^2 + M*(4.9m)^2?

    My question is - does the parallel-axis only work when we are moving the axis of rotation around "inside" the body or also outside it?
  2. jcsd
  3. Nov 25, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    It works inside or outside. I'd say that I = (2/5)MR^2 + M*D^2, where D is the distance from the center of mass to the desired axis.
  4. Nov 25, 2007 #3
    Of course, my bad - but thanks again. You have helped me very much.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook