Consider a system like the example problem where a batting machine swings a bat but instead of a baseball, the bat hits a lump of clay, which sticks to the end of the bat. How does the angular momentum of the clay and bat after the collision compare to the angular momentum of the clay and bat before the collision, and why?
It increases, the mass of the rotating object increases
It decreases, the velocity of the rotating object decreases
It decreases, momentum is lost in the collision
It stays the same, there is no external torque on the system
I said that it decreases because momentum is lost...that was wrong...
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Assuming that the collision happened so fast that the machine swinging the bat put no work in during the collision the angular momentum (of the entire bat/clay system)does not change. The moment of inertia is a little higher due to the mass of the clay so the angular velocity slows a bit, but the Angular momentum is the same before and after. Remember that not only the bat but the clay as well had angular momentum before the collision.
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