Question

A circular disc of mass $4kg$ and of radius $10cm$ is rotating about its natural axis at the rate of $5rad/sec$, its angular momentum is:

• A. $0.25kg{m}^2{s}^{-1}$
• B. $0.1kg{m}^2{s}^{-1}$
• C. $2.5kg{m}^2{s}^{-1}$
• D. $0.2kg{m}^2{s}^{-1}$

Answer 1

Answer: (B)

$0.1kg{m}^2{s}^{-1}$

m = 4 kg
R = 10 cm
$\omega =5rad/s$
$L=I\omega$
$=\frac{1}{2}M{R}^2\omega$
$=\frac{1}{2}\times 4\times (0.1{)}^2\times 5$
$=0.1kg{m}^2/s$