A disc of mass 2 Kg and radius 1 m rotates about its own axis with and angular speed 60 rpm. Find its kinetic energy and angular momentum .

Explanation

Angular speed `(omega ) = 60 rpm = 1 rpm = 2 pi rad * s^(-1) ` Moment of inertia of the disc `(I ) = (1)/( 2) Mr ^(2) `
[ where , M = mass of the disc , r= radius ]
` therfore ` rotaional kinetic energy `=(1)/(2) I Omega ^(2) = (1) /( 2) I Omega ^(2) = (1 ) /(2) I omega ^(2) = (1)/(2) * (1)/(2) Mr ^(2) omega ^(2) `
`= (1)/(4) xx 2 xx 1 xx ( 2pi )^(2)`
`= 2 pi ^(2) = 19.73 J`
Angular momentum `= I omega = (1)/(2) Mr ^(2) Omega =(1)/(2) xx 2 xx 1 ^(2) xx 2 pi `
`= 2 pi = 6.28 J.S `