Question

A cylinder has inner and outer radii of `12 cm` and `15 cm`, respectively, and a mass of `6 kg`. If the cylinder's frequency of rotation about its center changes from `7 Hz` to `3 Hz`, by how much does its angular momentum change?

Answer 1

The angular momentum changes by `0.93kgm^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=6*((0.12^2+0.15^2))/2=0.0369kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

The change in angular velocity is

`Delta omega=(7-3)*2pi=(8pi)rads^-1`

The change in angular momentum is

`DeltaL=0.0369*8pi=0.93kgm^2s^-1`