Angular Velocity of Two Attached Disks with Different Masses

[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.

 

[ONJ's Noble Steed]

Conservation of angular momentum!

 

[Harmeet Singh]

It would be approximtely 3.8 rad/s

 

[twjtiger]

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?