A solid disk of mass m1 = 9.3 kg and radius R = 0.22 m is rotating with a constant angular velocity of ω = 31 rad/s. A thin rectangular rod with mass m2 = 3.9 kg and length L = 2R = 0.44 m begins at rest above the disk and is dropped on the disk where it begins to spin with the disk.
What is the final angular velocity of the disk?
I know:
Initial Angular Momentum: 6.97
Initial Rotational Energy: 108.14

Question

A solid disk of mass m1 = 9.3 kg and radius R = 0.22 m is rotating with a constant angular velocity of ω = 31 rad/s. A thin rectangular rod with mass m2 = 3.9 kg and length L = 2R = 0.44 m begins at rest above the disk and is dropped on the disk where it begins to spin with the disk. 
What is the final angular velocity of the disk? 
I know:
Initial Angular Momentum: 6.97
Initial Rotational Energy: 108.14

anonymous · Answer

First, calculate total moment of inertia. Then apply conservation of angular momentum and rotational energy (Assuming that there is no change in energy when rod touches the disc.)

vincent-lyon.fr · Answer

Energy will not be conserved in this problem.