1. Limited time only! Sign up for a free 30min personal 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!

Yo-yo problem - rotational motion

  1. Dec 7, 2009 #1
    1. The problem statement, all variables and given/known data

    consider a yo-yo with R = 3.3 cm, r = 0.3 cm, and mass m = 84 g.

    What is the speed of the yo-yo after it has fallen a distance h = 1.20 m?

    What is the tension in the string while the yo-yo falls?

    What is the magnitude of the acceleration of the centre of mass as the yo-yo falls?

    2. Relevant equations

    L = Iw
    I = 0.5MR^2
    KEr = 0.5Iw^2
    Tnet = Ia

    3. The attempt at a solution

    change h into rotational displacement, not sure where to go or if thats even right.

    can anyone give me direction????
     
    Last edited: Dec 7, 2009
  2. jcsd
  3. Dec 7, 2009 #2
    would you solve this using conversation of energy?
     
  4. Dec 7, 2009 #3

    Delphi51

    User Avatar
    Homework Helper

    Yes, I would use energy for the first part. You have both rotational and translational energy and they are related by v = rω. The r = 0.3 cm must be the radius of the center "axel" that the string unwraps from.

    If you don't put in the h = 1.2 too soon, you'll have the speed as a function of h. Perhaps you can differentiate that with respect to time and get something you can use to find the acceleration.
     
  5. Dec 7, 2009 #4
    what would the moment of inertia be? 0.5mr^2, would you use the large or small radius?

    would the height be 1.2 m? for PE
     
  6. Dec 7, 2009 #5

    Delphi51

    User Avatar
    Homework Helper

    Yes, the large radius for moment of inertia.
    Yes, the initial height is 1.2 m.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Yo-yo problem - rotational motion
  1. Yo Yo Problem (Replies: 1)

  2. YO-YO Problem (Replies: 1)

  3. Yo-Yo problem (Replies: 0)

  4. Yo-Yo problem (Replies: 1)

  5. Yo-Yo problem (Replies: 1)

Loading...