Answer to Question #185647 in Classical Mechanics for Jethro

Question

What is the angular momentum of the hour hand of a clock If it has a length of 25 cm and a mass of 20 g?

Answer 1

$L= I*\omega,\text{where:}$

$I=\frac {ml^2}{3}-\text{Inertia of a thin bar the axis of rotation} \newline \text{passes through the end of the bar}\newline l=25cm =0.25m;\newline m=20g=0.02kg\newline I=\frac{0.02*0.25^2}{3}=4,16*10^{-4}$

$\omega-\text{angular velocity}\newline \text{one turn is }2\pi\ rad$

$\omega=\frac{2\pi}{t}$

$t=1h =3600s$

$\omega=\frac{2\pi}{3600}=1.75*10^{-3}$

$L=4.16*10^{-4}*1.75*10^{-3}=7.28*10^{-7}\newline \text{Answer: }7.28*10^{-7}\ \frac{kg*m^2}{s}$