Question

A cylinder has inner and outer radii of `5 cm` and `9 cm`, respectively, and a mass of `5 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `15 Hz` to `8 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum is `=1.17kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

Mass, `m=5kg`

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

So, `I=5*((0.05^2+0.09^2))/2=0.0265kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

The change in angular velocity is

`Delta omega=(15-8)*2pi=(14pi)rads^-1`

The change in angular momentum is

`DeltaL=0.0265*14pi=1.17kgm^2s^-1`