Question

A cylinder has inner and outer radii of `4 cm` and `9 cm`, respectively, and a mass of `7 kg`. If the cylinder's frequency of counterclockwise rotation about its center changes from `7 Hz` to `8 Hz`, by how much does its angular momentum change?

Answer 1

The change in angular momentum is `=0.21kgm^2s^-1`

Explanation:

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

and `omega` is the angular velocity

The change in angular momentum is

`Delta L=I Delta omega`

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

So, `I=7*(0.04^2+0.09^2)/2=0.03395kgm^2`

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

`Delta L=0.03395*2pi=0.21kgm^2s^-1`