Description
This is a simulation using two solid cylinders to demonstrate the concept of conservation of angular momentum.

The pink lower cylinder is on a frictionless, horizontal surface. The top blue cylinder is dropped onto the pink cylinder. Use the sliders to set the radius and height of each cylinder, the cylinder's mass will change accordingly. Set the initial angular velocity of each disk, as well as the coefficient of friction between the two disk. When you hit the "Run" button, the blue disk drops onto the pink disk and after some time, they eventually reach the same final rotational speed.

Click the "show numbers" checkbox to explore the numbers - see how the total energy changes, and notice how the total angular momentum of the system remains constant - as there are no external torques acting on anything in the system.