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Angular or Linear speed?

  1. Oct 25, 2006 #1
    A uniform solid ball rolls smoothly along a floor, then up a ramp inclined at 15.0°. It momentarily stops when it has rolled 1.50 m along the ramp.
    (a) What was its initial speed?

    First of all I'm assuming that the initial speed is the linear and not the angular speed is this right?

    Originally I was using Li=Lf where L=Iw however that is with angular speed and not linear speed. Would this problem involve using kinematics at all? What's throwing me off is which speed it is referring to. Any help is appreciated.
  2. jcsd
  3. Oct 25, 2006 #2
    Sounds like a conservation of energy problem. I'm guessing it is asking for translational velocity
  4. Oct 25, 2006 #3

    Doc Al

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    Staff: Mentor

    Since you are not given the ball's radius, all you can determine is the linear speed. (But since the ball rolls smoothly--without slipping--the linear and angular speeds are directly related.)
    Angular momentum is not conserved here--friction exerts a torque on the ball as it rolls up the incline.
    You certainly could solve this problem using kinematics (after figuring out the acceleration of the ball on the incline), but using conservation of energy will be easier.
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