Question

A solid disk, spinning counter-clockwise, has a mass of `8 kg` and a radius of `5/2 m`. If a point on the edge of the disk is moving at `13/4 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 `=204.2 kgms^-1`
The angular velocity is `=8.17rads^-1`

Explanation:

The angular velocity is

`omega=v/r`

where,

`v=13/4ms^(-1)`

`r=5/2m`

So,

`omega=(13/4)/(5/2)*2pi=13/5pi rad s^-1`

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

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

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

`L=13/5pi*25=204.2kgms^(-1)`