Question

A solid cylinder of mass 20 kg and radius 20 cm rotates about its axis with a angular speed 100 rads-1. The angular momentum of the cylinder about its axis is

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

Answer 1

Answer: (A)

40 Js

Answer 2

Here, M = 20 kg

R = 20 cm = 20 × $10 ^ { - 2 }$m, $\omega = 100 \mathrm { rad } \mathrm { s } ^ { - 1 }$

Moment of inertia of the solid cylinder about its axis is

$\mathrm { I } = \frac { \mathrm { MR } ^ { 2 } } { 2 } = \frac { ( 20 \mathrm {~kg} ) \left( 20 \times 10 ^ { - 2 } \mathrm {~m} \right) ^ { 2 } } { 2 } = 0.4 \mathrm {~kg} \mathrm {~m} ^ { 2 }$

Angular momentum of the cylinder about its axis is L =