Question

A cylinder has inner and outer radii of `8 cm` and `12 cm`, respectively, and a mass of `8 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `1 Hz` to `7 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum is `=3.14kgm^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=8*(0.08^2+0.12^2)/2=0.0832kgm^2`

The change in angular velocity is

`Delta omega=(7-1)*2pi=12pirads^-1`

The change in angular momentum is

`DeltaL=IDelta omega`

`=0.0832*12pi=3.14kgm^2s^-1`