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: Rotational Kinetic

  1. Nov 14, 2006 #1
    Use conservation of energy to determine the angular speed of the spool shown in Figure P8.36 after the 3.00 kg bucket has fallen 4.65 m, starting from rest. The light string attached to the bucket is wrapped around the spool and does not slip as it unwinds.

    I used conservation of energy.
    (KEr + KEt + mgh)i = (KEr + KEt + mgh)f
    0 + 0 + (3 x 9.8 x 4.65) = [.5(.5Mr^2)w^2] + .5(Mv^2) + 0
    136.71 = (.25Mr^2)w^2 + .5Mv^2
    136.71 = (.25 x 5 x v^2) + (.5 x 5 x v^2)
    v = 7.39
    w = 12.324

    The ans is not correct, what am i doin wrong?

    Thank you for lookin but I manage to see my mistake. I used the wrong mass for the KEt
     

    Attached Files:

    Last edited: Nov 14, 2006
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted