Question

A cylinder has inner and outer radii of `5 cm` and `11 cm`, respectively, and a mass of `5 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `12 Hz` to `6 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum is `=1.376kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

For the cylinder, `I=m(r_1^2+r_2^2)/2`

So, `I=5*(0.05^2+0.11^2)/2=0.0365kgm^2`

The change in angular velocity is

`Delta omega=(12-6)*2pi=12pirads^-1`

The change in angular momentum is

`DeltaL=IDelta omega`

`=0.0365*12pi=1.376kgm^2s^-1`