Linear and angular momentum problem

AI Thread Summary
The discussion revolves around a physics problem involving a thin bar and a blob of putty colliding on a frictionless surface. The user seeks assistance in setting up the problem to find the velocity of the system's center of mass and the angular speed after the collision. Key points include the use of conservation of angular momentum to derive the equations and the importance of calculating angular momentum about the center of mass of the combined system. The conversation highlights the need to consider the center of mass location for accurate calculations following the collision. The user expresses understanding of the concept after receiving clarification on the rotation dynamics involved.
barryj
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This is not a homework problem.
I am trying to set up the following problem. I am doing something wrong. Help. I have attached the problem and figure but here is the text.

Figure 10-52 shows a thin, uniform bar of Length L and mass M and a small blob of putty of mass m. The system is supported by a frictionless horizontal surface. The putty moves to the right with a velocity v, strikes the bar at a distance d from the center of the bar, and sticks to the bar at the point of contact. Obtain expression for the velocity of the system's center of mass and for the angular speed following the collision.

To find the angular speed, I use the conservation of angular momentum.

mv(1)d = m*v(2)*d + (1/12)ML^2 * V(2)

Is this a correct setup?

Thanks
Barry
 

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Compute the angular momentum about the center of mass of the system.
 
Thanks Doc Al, I think I see your point. When the putty hits the bar, the rotation is about the center of mass of the rod/putty combination and will be between the center of the rod and the putty as I how on my attachment. Yes?
 

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barryj said:
Thanks Doc Al, I think I see your point. When the putty hits the bar, the rotation is about the center of mass of the rod/putty combination and will be between the center of the rod and the putty as I how on my attachment. Yes?
Yes, that's correct. Now figure out the speed of the bullet and the bar in the center of mass frame.
 
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