Two disks of identical mass but different radii (r and 2r) are spinning on frictionless bearings at the same angular speed ω(adsbygoogle = window.adsbygoogle || []).push({}); _{o}, but in opposite directions. The two disks are brought slowly together. The resulting frictional force between the surfaces eventually brings them to a common angular velocity.

(a) What is the magnitude of that final angular velocity in terms of ω_{o}

[tex]\frac{3}{5}[/tex]ω_{o}< - I know that's right.

(b) What is the change in rotational kinetic energy of the system? (Take K as the initial kinetic energy.) This is what I need help with.

I used Ke=Iω^{2}, coupled the system, considered one direction negative and one positive, and got [tex]\frac{9}{50}[/tex]mr^{2}ω_{o}^{2}, which is apparently wrong. . .

Thank you ahead of time!

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# Homework Help: Conservation of angular momentum / finding change in rotational kinetic energy

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