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: Angular momentum/angular velocity.

  1. Dec 17, 2008 #1
    1. The problem statement, all variables and given/known data

    1.A solid, vertical cylinder of mass 10.0 kg and radius 1.00 m rotates with an angular speed of 7.00 rad/s about a fixed vertical axis through its center. A .250 kg piece of putty is dropped vertically onto the cylinder at a point 0.900 m from the center of ration and sticks to the cylinder. Determine the final angular speed of the system.


    2. Relevant equations

    Lbefore=Lafter
    L=Iw

    3. The attempt at a solution

    the angular momentum is L and the angular velocity is what i am looking for that is w.
    I beleive you can say that IoWo should = IW

    I am unsure what you are to do with the mass of the putty and the center of radian issue.

    I believe you need to set up taht W = (Io/I)wo

    Io = MR^2???
     
  2. jcsd
  3. Dec 17, 2008 #2
    [tex] I_{o}\times \omega_{o}=I_{f}\times \omega_{f} [/tex]

    We know [tex] I_{o}= \frac{1}{2}MR^2 [/tex] plus we know wf

    [tex] I_{f}=\frac{1}{2}MR^2+mr^2 [/tex]
    Note: the [tex] I_{f} [/tex] changes, the parallel axis theorm is used.

    only [tex] \omega_f [/tex] left that's unknown.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook