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!

Radius of Gyration?

  1. Oct 28, 2012 #1
    1. The problem statement, all variables and given/known data
    TzlCO.png

    3. The attempt at a solution
    Alright, so the solution manual shows that the intertia of the disk is:
    I = m * k2, where k is the radius of gyration​

    However why can't the inertia of the disk be:
    I = 0.5 * m * r2, where r is the radius of the disk​
    This is the formula for the inertia of a rotating disk... However when I plug in all my numbers I get a different inertia value when compared to the inertia value that I got using the radius of gyration.
     
  2. jcsd
  3. Oct 28, 2012 #2

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Because the spool is not a uniform disk. You don't need to know why it's not uniform, just accept that you are given the effective radius.
     
  4. Oct 28, 2012 #3
    Ah okay, I wish it said that the density is not uniformly distributed... But thanks!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Radius of Gyration?
  1. Radius of Gyration (Replies: 1)

Loading...