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

1. Apr 12, 2015

### Westin

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?

2. Relevant equations
Cross Product

3. The attempt at a solution

τ⃗ A=r⃗ A×F⃗
Cross Product

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

### robphy

3. Apr 12, 2015

### Westin

Am I correct?

4. Apr 12, 2015

### robphy

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
5. Apr 13, 2015

### paisiello2

Right hand rule?