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Homework Help: Rolling and sliding sphere on flat surface

  1. Sep 4, 2011 #1
    1. The problem statement, all variables and given/known data

    In a laboratory experiment two spherical balls are launched on a °at surface. Both are
    uniform spheres of radius R and mass m. They are both given the same amount of
    initial kinetic energy K0. However:
    -ball A rolls without slipping
    -ball B slides without rotating
    What is the ratio Vb/Va?

    2. Relevant equations
    Moment of inertia of solid sphere= 2/5 (mr^2)

    3. The attempt at a solution
    for the rotating, I did

    KErolling=1/2 mv^2 = 1/2 Iw^2 => KEo = 7/10 mv^2

    then for the slipping, I'm having a bit of problem. I am not sure if i have to include the friction force or not. Without friction, it'd be F=ma, then KEo=ma, I'm not sure if i can substitute KEo as F or not..

  2. jcsd
  3. Sep 4, 2011 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Since B slides without rotating, the friction force must be zero.
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