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Homework Help: Angular speed question

  1. Nov 6, 2009 #1
    1. The problem statement, all variables and given/known data

    A 320 N sphere 0.20 m in radius rolls, without slipping, 6.0 m down a ramp that is inclined at 25° with the horizontal. What is the angular speed of the sphere at the bottom of the hill if it starts from rest?

    2. Relevant equations
    I sphere= (2/5)mr^2
    atan=rα
    v=rω

    3. The attempt at a solution
    I tried first to use F∆x=(1/2)*[(2/5)mr^2]ωf^2-0(zero because it starts from rest) but then i realize i don't have a mass and now i don't really know what to do. any helpful hints or suggestions would be appreicated
     
  2. jcsd
  3. Nov 6, 2009 #2

    rock.freak667

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    At the top, it only has potential energy mgh. At the bottom, the energy is entirely kinetic. Do you see why you don't need the mass?
     
  4. Nov 6, 2009 #3
    so then can i just solve the eqn i was using and just ignore m?
     
  5. Nov 6, 2009 #4

    rock.freak667

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    No your equation is correct. Just what is the force F in [itex]F\Delta x[/itex]?
     
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