# Homework Help: Collision between ball and stick

1. Apr 29, 2010

### juggalomike

1. The problem statement, all variables and given/known data
On a frictionless table, a 0.58 kg glob of clay strikes a uniform 1.62 kg bar perpendicularly at a point 0.18 m from the center of the bar and sticks to it. If the bar is 0.70 m long and the clay is moving at 6.20 m/s before striking the bar, what is the final speed of the center of mass?
A=1.63m/s

At what angular speed does the bar/clay system rotate about its center of mass after the impact?
A=?

[PLAIN]http://img217.imageshack.us/img217/616/prob21a.gif [Broken]

2. Relevant equations

Not sure

3. The attempt at a solution

I solved for the final speed of the center of mass using conservation of momentum, but i am lost on the 2nd part. I know the center of mass changes when the clay is attached to the bar, but im not sure how i would use that to solve the question.

Last edited by a moderator: May 4, 2017
2. Apr 29, 2010

### tiny-tim

Hi juggalomike!

Use conservation of angular momentum …

what do you get?

3. Apr 29, 2010

### juggalomike

If i using conservation of angular momentum, which is Ii*Wi=If*Wf the initial side will be 0 because initialy it has no angular velocity?

4. Apr 29, 2010

### collinsmark

Hello juggalomike,

Think about what is the center of mass of the system (the system being the combination of bar and glob) immediately before impact. Using that point as the center of mass, what is angular momentum (before impact) associated with the bar? And the glob?

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