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?

1 Answer
Jul 19, 2017

Answer:

#ΔL=-0.008pi(kgm^2)/s#

Explanation:

The moment of inertia for the cylinder in your problem in :

#I=1/2m(r^2+R^2)=1/2*1*(0.02^2+0.04^2)=0.001kgm^2#

Let's calculate the change in angular velocity :

#Δω=2piΔf=2pi4=8pi(rads)/s#

Now let's caclulate the change in angular momentum :

#ΔL=IΔω=0,001*8π=0.008pi(kgm^2)/s#

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

#ΔL=-0.008pi(kgm^2)/s#