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Homework Help: Ball up an incline

  1. Dec 9, 2006 #1
    http://img207.imageshack.us/img207/5524/untitledll1.png [Broken]

    what i'm looking for is 1. the total energy of the sphere, and 2. the height of the ball after it has traveled up the incline.

    i have some questions however. First, i understand that total energy = KE+PE. looking at the solution, KE=1/2mv^2. why does PE=1/1*Iw^2? this is the first time i've ever seen PE defined as such an equation.

    in the second part of the solution, they use mgh - why isn't mgh used in the first solution? thanks
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Dec 9, 2006 #2


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    The term 'PE=1/1*Iw^2' you were referring to was supposed to be the rotational kinetic energy of the sphere, which equals 1/2 I w^2, so I assume it was a mistype. You're right - total energy is defined as the sum of potential and kinetic energy - but, since you have a rolling sphere, the kinetic energy is the sum of rotational and translational kinetic energy.
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