A solid cylinder of mass 3 kg and radius 10 cm is rotating about its axis with a frequency `20//pi`. The rotational kinetic energy of the cylinder

Options

A. `10 pi J`
B. `12 J`
C. `(6xx10^(2))/(pi)J`
D. 3J

Answer

B

Explanation

Given `M=3kg R=0.1m v=20//pi`
Angular frequency `omega=2piv=(2pixx20)/(pi)=40 "rad"//s^(-1)`
Moment offerta of the cylinder about its axis `=I=(1)/(2) mR^(2)xx3xx(0.1)^(2)=0.015 kg m^(2)`
`K.F=(1)/(2) I omega^(2)=(1)/(2)xx0.015xx(40)^(2)=12 J`