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A ball of mass m is thrown with a velocity v at a disk

  1. Apr 12, 2015 #1
    1. The problem statement, all variables and given/known data

    A ball of mass m is thrown with a velocity v at a disk of mass M which sticks to the rim on impact.


    https://s3.lite.msu.edu/res/msu/perl_author/P3_PRELECTURE/L_CONSERVATION/IMAGES/CQ1.png

    For the system of the ball and disk, what is the total initial angular momentum about the axis?


    [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,0,Rmv[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png [Broken]
    [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,0,−Rmv[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png [Broken]
    [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,−Rmv,0[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png [Broken]
    [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,Rmv,0[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png [Broken]
    [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,0,0[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png[/B] [Broken]

    2. Relevant equations
    Cross Product

    3. The attempt at a solution

    τ⃗ A=r⃗ A×F⃗
    Cross Product
    [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,0,−Rmv[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png [Broken]
     

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    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Apr 12, 2015 #2

    robphy

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    What is your specific question about this question?
     
  4. Apr 12, 2015 #3
    Am I correct?
     
  5. Apr 12, 2015 #4

    robphy

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    Yes, [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png0,0,−Rmv[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.png, [Broken] using the definition of angular momentum as L=r x p and the right-hand rule (presuming the axis is through the axis of the disk).
     
    Last edited by a moderator: May 7, 2017
  6. Apr 13, 2015 #5
    Right hand rule?
     
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