Question

A solid cylinder of mass $20kg$ and radius $20cm$ rotates about its axis with an angular speed of $100rad{s}^{-1}$ . The angular momentum of the cylinder about its axis is

• A. $40Js$
• B. $400Js$
• C. $20Js$
• D. $200Js$

Answer 1

Answer: (A)

Here, $M=20kg$ $R=20cm=20\times 10^{-2}m,\omega =100rad{s}^{-1}$
Moment of inertia of the solid cylinder about its axis is
$I=\frac{M{R}^2}{2}=\frac{(20kg)(20\times 10^{-2}m{)}^2}{2}=0.4kg{m}^2$
Angular momentum of the cylinder about its axis is
$L=I\omega =(0.4kg{m}^2)(100rad{s}^{-1})=40Js$