Question

A cylinder has inner and outer radii of `9 cm` and `12 cm`, respectively, and a mass of `2 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `24 Hz` to `18 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum is `=0.85kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

Mass, `m=2kg`

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

So, `I=2*((0.09^2+0.12^2))/2=0.0225kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

The change in angular velocity is

`Delta omega=(24-18)*2pi=(12pi)rads^-1`

The change in angular momentum is

`DeltaL=0.0225*12pi=0.85kgm^2s^-1`