Question

A solid disk, spinning counter-clockwise, has a mass of `1 kg` and a radius of `5 m`. If a point on the edge of the disk is moving at `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 `=62.8kgms^(-1)`
The angular velocity is `=(8pi)/5 rad s^(-1)`

Explanation:

The angular velocity is

`omega=v/r`

where,

`v=4ms^(-1)`

`r=5m`

So,

`omega=4/5*2pi=(8pi)/5 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=1*5^2/2=25/2=12.5kgm^2`

`L=12.5*8/5pi=20pi=62.8kgms^(-1)`