Answer
(a) $L=10.1 \frac{Kgm^2}{s}$
(b) $\tau=-2.5Nm$
Work Step by Step
(a) We can find the angular momentum as
$L=I\omega$
$L=\frac{1}{2}mr^2\omega$ (Because moment of inertia$I=mr^2$)
We plug in the known values to obtain:
$L=\frac{1}{2}(48)(0.15)^2(3)(2\pi)=10.1\frac{Kg m^2}{s}$
(b) We can find the torque as:
$\tau=\frac{\Delta L}{\Delta t}$
We plug in the known values to obtain:
$\tau=\frac{0-10.1}{4}=-2.5Nm$
