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: Normal modes

  1. Mar 13, 2005 #1
    Dear friends,

    I'm having trouble with this problem, I don't know if I'm doing it right, I'd be grateful if you could advice me.

    Two discs, each of mass M and radius R, are supported with equal
    separation along a slender rod to which they are rigidly fastened at
    their centers as shown in the picture I attached below.

    I need to calculate the normal frequencies and normal modes.

    This is what I've done:

    T(kinetic energy)=1/2*1/2MR^2(theta1^2+theta2^2)
    V(potential)=1/2*k(theta1^2+theta2^2+(theta1-theta2)^2

    Where theta is the angle the disc turns. Does this make sense?

    THanks!
     

    Attached Files:

    Last edited: Mar 13, 2005
  2. jcsd
  3. Mar 13, 2005 #2
    well,

    If what mentioned above is right, I found out that either in phase or counterphase are the system's normal modes.

    The thing is that, at the beginning both discs start from 0 but disc number 2 has an initial velocity u. I am asked to describe the motion and calculate how long it will take the first disc to get all KINETIC ENERGY.

    Don't solve the problem for me, but just give me a hint what I should do.

    THanks
     
  4. Mar 13, 2005 #3
    is it possible that disc 1 can receive all the kinetic energy?
     
  5. Mar 13, 2005 #4
    please. I need help
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook