A cylinder has inner and outer radii of #2 cm# and #4 cm#, respectively, and a mass of #1 kg#. If the cylinder's frequency of counterclockwise rotation about its center changes from #6 Hz# to #2 Hz#, by how much does its angular momentum change?
The moment of inertia for the cylinder in your problem in :
Let's calculate the change in angular velocity :
Now let's caclulate the change in angular momentum :
To start with the angular momentum was a vector that was comming out of the screen if the cylinder was on the screen.
Now that its lowered the change is into the page so we mus have