Question

A cylinder has inner and outer radii of `8 cm` and `15 cm`, respectively, and a mass of `3 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `15 Hz` to `12 Hz`, by how much does its angular momentum change?

Answer 1

The angular momentum changes by `=0.82kgm^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=3*(0.08^2+0.15^2)/2=0.04335kgm^2`

The change in angular velocity is

`Delta omega=(15-12)*2pi=6pirads^-1`

The change in angular momentum is

`DeltaL=IDelta omega`

`=0.04335*6pi=0.82kgm^2s^-1`