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Homework Help: Find translational Ke Rotational Ke

  1. Dec 9, 2006 #1
    1. The problem statement, all variables and given/known data

    A basketball weighs 500grams or (.5 kg) it has a radius of 10cm (.10 m) and is rolling at 2.0 m/s. Find translational Ke Rotational Ke Translational momentum and Rotational momentum.


    2. Relevant equations
    translational ke= 1/2mv^2
    rotational ke = 1/2Iw^2 ( I am unsure of what inertia equation to use for a basketball)
    Translational momentum= mv^2
    rotational ke = iw
    3. The attempt at a solution

    Translational ke = 1/2 mv^2= .5(.5kg)(2.0m/s)^2= 1 J
    I think I know how to do the equations I just dont know what equation to use for the rotational inertia for a basketball, if someone could help me on that. Thanks :redface:
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Dec 9, 2006 #2

    Andrew Mason

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    I think you mean L = angular momentum = [itex]I\omega[/itex]
    The moment of inertia of a solid or hollow sphere is a calculus problem. It works out to [itex]\frac{2}{5}MR^2[/itex] for a solid sphere and [itex]\frac{2}{3}MR^2[/itex] for a hollow sphere (see the http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#cmi"). Which one would you use?

    How do you determine the rotational speed from the translational speed? ie. how long does it take the ball to roll 360 degrees or [itex]2\pi[/itex] radians?

    AM
     
    Last edited by a moderator: Apr 22, 2017
  4. Dec 9, 2006 #3

    radou

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    This should serve as a clue: http://www.physics.upenn.edu/courses/gladney/mathphys/java/sect4/subsubsection4_1_4_3.html" [Broken].

    Edit: oops, late.
     
    Last edited by a moderator: May 2, 2017
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