Question

A cylinder has inner and outer radii of `9 cm` and `16 cm`, respectively, and a mass of `6 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `9 Hz` to `3 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum is `=3.81kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

Mass, `m=6kg`

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

So, `I=6*((0.09^2+0.16^2))/2=0.1011kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

The change in angular velocity is

`Delta omega=(9-3)*2pi=(12pi)rads^-1`

The change in angular momentum is

`DeltaL=0.1011*12pi=3.81kgm^2s^-1`