Question

A solid disk, spinning counter-clockwise, has a mass of `18 kg` and a radius of `4 m`. If a point on the edge of the disk is moving at `7/3 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 `=527.8 kgm^2s^(-1)`
The angular velocity is `=3.7 rads^(-1)`

Explanation:

The angular velocity is

`omega=v/r`

`v=7/3ms^(-1)`

`r=4m`

`omega=7/3*1/4*2pi=(7pi)/6rads^(-1)`

The angular momentum is `L=Iomega`

Where `I` is the moment of inertia

For a solid disc `I=mr^2/2=18*4^2/2=144 kgm^2`

The angular momsntum is
`L=Iomega=144*7pi/6=168pi kgm^2s^(-1)`