A solid cylinder of mass `20 kg` rotates about its axis with angular speed `100 s^(-1)`. The radius of the cylinder is `0.25 m`. What is the kinetic energy associated with the rotation of the cylinder ? What is the magnitude of angular momentum of the cylinder about its axis ?

Options

A. `3200J, 62.5 J-s`
B. `3125J, 62.5 J-s`
C. `3500 J, 68 J-s`
D. `3400 J, 63.3J-s`

Answer

B

Explanation

Moment of inertia of the solid cylinder about its axis of symmetry,
`l=(1)/(2)MR^(2)=(1)/(2)xx2xx(0.25)^(2)`
`=10xx0.0625=0.625kg-m^(2)`
Kinetic energy associated with the rotation of the sylinder is given by
`K=(1)/(2)l omega^(2)=(1)/(2)xx0.625xx(100)^(2)`
`=03125xx10000=3125J`
Angular momentum, `L=l omega=0.625xx100=62.5J-s`