Question

A cylinder has inner and outer radii of `4 cm` and `18 cm`, respectively, and a mass of `1 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `15 Hz` to `9 Hz`, by how much does its angular momentum change?

Answer 1

The change in ngular momentum is `=0.64kgm^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=1*((0.04^2+0.18^2))/2=0.017kgm^2`

The change in angular velocity is

`Delta omega=(15-9)*2pi=12pirads^-1`

The change in angular momentum is

`DeltaL=IDelta omega`

`=0.017*12pi=0.64kgm^2s^-1`