Question

A solid disk, spinning counter-clockwise, has a mass of `14 kg` and a radius of `5/4 m`. If a point on the edge of the disk is moving at `2/9 m/s` in the direction perpendicular to the disk's radius, what is the disk's angular momentum and velocity?

Answer 1

The angular momentum is `=12.22kgm^2s^(-1)`
The angular velocity is `=1.12rads^-1`

Explanation:

The angular velocity is

`omega=v/r`

where,

`v=2/9ms^(-1)`

`r=5/4m`

So,

`omega=(2/9)/(5/4)*2pi=16/45pi=1.12rads^-1`

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

For a solid disc, `I=(mr^2)/2`

So, `I=14*(5/4)^2/2=175/16kgm^2`

`L=1.12*175/16=12.22kgm^2s^(-1)`