An solid cylinder of mass `20 kg` and radius `20 cm` rotates about its axis with a angular speed `100 rad s^-1`. The angular momentum of the cylinder about its axis is.

Options

A. 40 J s
B. 400 J s
C. 20 J s
D. 200 J s

Answer

A

Explanation

Here, M=20 kg
R= 20 cm = `20 xx 10^(-2)m, omega=100 rad s^(-1)`
Moment of inertia of the solid cylinder about its axis is
`I=(MR^(2))/(2) = (20kg)(20 xx 10^(-2) m)^(2)/(2) = 0.4 kg m^(2)`
Angular momentum of the cylinder about the axis is
`L=Iomega = (0.4 kg m^(2)) (100 rad s^(-1)) = 40 Js`