Question

A cylinder has inner and outer radii of `4 cm` and `5 cm`, respectively, and a mass of `5 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `7 Hz` to `9 Hz`, by how much does its angular momentum change?

Answer 1

The change in the angular momentum is `=0.13kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

The mass, `m=5kg`

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

So, `I=5*((0.04^2+0.05^2))/2=0.01025kgm^2`

The change in angular momentum is

`DeltaL=IDelta omega`

The change in angular velocity is

`Delta omega=(9-7)*2pi=(4pi)rads^-1`

The change in angular momentum is

`DeltaL=0.01025*4pi=0.13kgm^2s^-1`