# Chapter 8 - Rotational Motion - Problems: 63

The final angular speed is half of the initial angular speed.

#### Work Step by Step

There is no net external torque on the system, so the net angular momentum is conserved. The two disks have the same angular velocity at the end. $$L_i=L_f$$ $$I \omega_i + I(0)=2I \omega_f$$ $$\omega_f=\frac{1}{2}\omega_i$$

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