Question

A cylinder has inner and outer radii of `16 cm` and `21 cm`, respectively, and a mass of `2 kg`. If the cylinder's frequency of rotation about its center changes from `4 Hz` to `9 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum `=2.19kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

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

So, `I=2*(0.16^2+0.21^2)/2=0.0697kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

`Delta omega=(9-4)*2pi=10pirads^-1`

`DeltaL=0.0697*10pi=2.19kgm^2s^-1`