Question

A cylinder has inner and outer radii of `2 cm` and `12 cm`, respectively, and a mass of `2 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 `=0.28kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

The mass, `m=2kg`

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

So, `I=2*((0.02^2+0.12^2))/2=0.0148kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

The change in angular velocity is

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

The change in angular momentum is

`DeltaL=0.0148*6pi=0.28kgm^2s^-1`