Question

A solid disk, spinning counter-clockwise, has a mass of `16 kg` and a radius of `3/8 m`. If a point on the edge of the disk is moving at `7/5 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 `=4.2kgm^2s^-1`
The angular velocity is `=3.73rads^-1`

Explanation:

The angular velocity is

`omega=(Deltatheta)/(Deltat)`

`v=r*((Deltatheta)/(Deltat))=r omega`

`omega=v/r`

where,

`v=7/5ms^(-1)`

`r=3/8m`

So,

`omega=(7/5)/(3/8)=56/15=3.73rads^-1`

The angular momentum is `L=Iomega`

where `I` is the moment of inertia

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

So, `I=16*(3/8)^2/2=9/8kgm^2`

`L=56/15*9/8=4.2kgm^2s^-1`