# A solid disk, spinning counter-clockwise, has a mass of 3 kg and a radius of 3 m. If a point on the edge of the disk is moving at 8 m/s in the direction perpendicular to the disk's radius, what is the disk's angular momentum and velocity?

##### 1 Answer
Oct 25, 2016

The disc angular momentum is $36 k g {m}^{2} {s}^{- 1}$
And the angular velocity is $\left(\frac{8}{3}\right) \frac{r a d}{s}$

#### Explanation:

The angular momentum is given by L=I×omega
Where $I =$moment of inertia
And $\omega =$angular velocity

The moment inertia of a disc is given by $I = \frac{m {r}^{2}}{2}$
where $m =$ mass of the disc
And $r =$radius of the disc

Also we use the formula $v = r . \omega$

So $\omega = \frac{v}{r} = \frac{8}{3} r a \frac{d}{s}$

$I = {3.3}^{2} / 2 = \frac{27}{2} k g {m}^{2}$

And the angular momentum is $L = \frac{27}{2.} \left(\frac{8}{3}\right) = 36 k g {m}^{2} {s}^{- 1}$