Angular Velocity of Two Attached Disks with Different Masses

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To determine the angular velocity of two attached disks with different masses, conservation of angular momentum is applied. The first disk has a mass of 5.0 kg and an angular velocity of 10.0 rad/sec, while the second disk has a mass of 8.0 kg and is dropped onto the first. The combined angular momentum before and after they attach must be equal, leading to the calculation of the new angular velocity. The resulting angular velocity of the system is approximately 3.8 rad/s. The approach using the moment of inertia formula is correct for setting up the conservation equation.
twjtiger
Another one that I can't figure out.

A solid disk of mass 5.0 kg and a radius of 15.0 cm is rotating with a constant angular velocity of 10.0 rad/sec. Another disk, with the same radius but a mass of 8.0 kg, is slowly dropped upon the first disk until they rotate together. Determine the angular velocity of the system after the two disks are attached.
 
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Conservation of angular momentum!
 
It would be approximtely 3.8 rad/s
 
Would I start with

1/2 MR(Sqared)=1/2 MR(Squared)

That would set the two disks equal to each other. Would this be correct?
 
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