A uniform circular disc of mass 200 g and radius 4.0 cm is rotated about one of its diameter at an angular speed of 10 rad/s. Find the kinetic energy of the disc and its angular momentum about the axis of rotation.

Explanation

The moment of inertia of the circular disc about its diameter is
`I=1/4Mr^2=1/4(0.200kg)(0.04m)^2`
`=8.0xx10^-5kg-m^2`
the kinetic energy is
`K=1/2Iomega^2=1/2(8.0xx10^-5kgm^2)(100rad^2/s^2)`
`=4.0xx10^-3J`
and the angular momentum abotu the axis of rotation is
`L=Iomega=(8.0xx10^-5kg-m^2)(10rad/s)`
`=8.0xx10^-4kg-m^2/s=8.0xx10^-4J-s`