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!

Angular momentum (two discs).

  1. Jan 6, 2007 #1
    a disc with moment of inertia I1 turns around its axis which passes through its centre with an angular velocity of w0. we attach to it another disc with moment of inertia I2 (at first it doesnt spin), as a result of friction between the discs they achieve a combined angular velocity of w.
    i need to find the combined angular velocity, w?
    how much mechanical velocity was lost in the process.

    basically i think i need to use here conversion of angular momentum, i.e the a.m before is I1w0, my problem is what the angular momentum after we add the second disc, i think it's I2w+I1w am i correct here?
    if so then I1w0=(I1+I2)w.
    and to calculate the loss of energy we have:
    1/2I1w0^2-1/2(I1+I2)w^2, right?
    Last edited: Jan 6, 2007
  2. jcsd
  3. Jan 6, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Assuming they rotate about the same axis, yes you are correct.
  4. Jan 7, 2007 #3
    yes they rotate about the same axis.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?