Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help review for test please.

  1. Nov 9, 2006 #1
    im stuck on one of the homework problems im reviewing for a test. any help would be appreciated. im not sure on how to set up the problem.

    a small 1.32 kg mass is connected to a cord of length 1.62 meters, and spun at a constant angular speed of 8.0 radians per second. if the cord is pulled inward so that the mass is only 0.33 times as far from the axis as it started out, what is the final angular speed of the mass at its new distance from the axis?
  2. jcsd
  3. Nov 9, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    HINT: Conservation of angular momentum
  4. Nov 9, 2006 #3
    thats what i was thinking.. so i would set them equal.. what would the moment of inertia be for this case?
  5. Nov 9, 2006 #4


    User Avatar

    Since the mass is small, [tex]I = mr^2[/tex], where r is the length of the cord.
  6. Nov 9, 2006 #5
    oh ok. i got it

    since the mass would cancel out i got r1^2*v1=r2^2*v2 with the answer 73.46radians per second.

    is that correct?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook