A solid disk, spinning counter-clockwise, has a mass of #5 kg# and a radius of #4 m#. If a point on the edge of the disk is moving at #7 m/s# in the direction perpendicular to the disk's radius, what is the disk's angular momentum and velocity?

1 Answer
Dec 18, 2016

Answer:

The angular momentum is #L=(140pi) kgm^2s^(-1)#
The angular velocity is #omega=(7/2pi) rads^(-1)#

Explanation:

The angular velocity is #omega=v/r#

#v=7ms^(-1)#

#r=4m#

So,

#omega=7/4*2pi rads^(-1)=7/2pi rads^(-1)#

The angular momentum is #L=Iomega#

Where,

#I=# moment of inertia

For a solid disc, #I=1/2mr^2#

#I=1/2*5*4*4=40 kgm^2#

The angular momentum is

#L=Iomega=40*7/2pikgm^2s^(-1)#

#L=140pi kgm^2s^(-1)#