Question

A solid disk, spinning counter-clockwise, has a mass of `6 kg` and a radius of `8/5 m`. If a point on the edge of the disk is moving at `12/5 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 `=72.4kgms^(-1)`
The angular velocity is `=9.42rads^-1`

Explanation:

The angular velocity is

`omega=v/r`

where,

`v=12/5ms^(-1)`

`r=8/5m`

So,

`omega=(12/5)/(8/5)*2pi=3pi=9.42rads^-1`

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

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

So, `I=6*(8/5)^2/2=192/25kgm^2`

`L=9.42*192/25=72.4kgms^(-1)`