Angular momentum problem

1. May 3, 2007

neelakash

1. The problem statement, all variables and given/known data

Two masses M each are connected by a rigid rod of negligible mass having length a.The CM of the system is stationary in a gravity free space and the system rotates about the CM. with angular velocity w.One of the rotating masses strikes a third stationary ball of mass M which sticks to it.What is the angular momentum of the three mass system before and after collision?

2. Relevant equations

3. The attempt at a solution

For the collision conservation of linear momentum will be applicable.
Mv=2Mv' or,v'=v/2=wa/4. From this w' can be calculated.

Prior collision,L=Iw where I is the MI of the two mass system.

After collision, L'=I'w'

Please check if I am correct.

2. May 3, 2007

mukundpa

the system will rotate about new center of mass. Check for the position of new center of mass!!

3. May 3, 2007

neelakash

So,we are to be careful to calculate I for the second time.
Second time, CM will be a/3 rd distance away from the mass 2M.Accordingly,I will change.

But angular velocity would be same as w'.Right?

4. May 3, 2007

neelakash

There will be no linear momentum...
angular momentum will be conserved...
CM will change the position...
And if one wants to find w',one has to find I' carefully.